AU2020290835A1

AU2020290835A1 - Image decoding method for deriving weight index information for bi-prediction, and device for same

Info

Publication number: AU2020290835A1
Application number: AU2020290835A
Authority: AU
Inventors: Hyeongmoon JANG; Junghak NAM; Naeri PARK
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2019-06-14
Filing date: 2020-06-10
Publication date: 2022-02-10
Anticipated expiration: 2040-06-10
Also published as: KR20240012613A; KR20210153736A; US11973938B2; AU2020290835B2; CA3143546A1; EP3982635A1; JP2023154003A; WO2020251259A1; CN114145022A; JP7331154B2; KR102627935B1; EP3982635A4; US11457209B2; US20230018123A1; US20220150472A1; JP2022537168A; AU2024201477A1

Abstract

According to the disclosure of the present document, when the inter-prediction type of the current block indicates bi-prediction, weight index information for a candidate in a merge candidate list or sub-block merge candidate list can be derived, and coding efficiency can be raised.

Description

IMAGE DECODING METHOD FOR DERIVING WEIGHT INDEX INFORMATION FOR BIPREDICTION, AND DEVICE FOR SAME BACKGROUND OF THE DISCLOSURE

Field of the disclosure

[11 The present disclosure relates to an image decoding method and apparatus for deriving

weight index information on bi-prediction.

Related Art

[2] Recently, the demand for high resolution, high quality image/video such as 4K, 8K or

more Ultra High Definition (UHD) image/video is increasing in various fields. As the

image/video resolution or quality becomes higher, relatively more amount of information or

bits are transmitted than for conventional image/video data. Therefore, if image/video data are

transmitted via a medium such as an existing wired/wireless broadband line or stored in a

legacy storage medium, costs for transmission and storage are readily increased.

[3] Moreover, interests and demand are growing for virtual reality (VR) and artificial

reality (AR) contents, and immersive media such as hologram; and broadcasting of

images/videos exhibiting image/video characteristics different from those of an actual

image/video, such as game images/videos, are also growing.

[4] Therefore, a highly efficient image/video compression technique is required to

effectively compress and transmit, store, or play high resolution, high quality images/videos

showing various characteristics as described above.

SUMMARY

[5] The present disclosure provides a method and an apparatus for increasing image coding efficiency.

[6] The present disclosure also provides a method and apparatus for deriving weight index

information on bi-prediction in inter-prediction.

[7] The present disclosure also provides a method and apparatus for deriving weight index

information on a candidate in an affine merge candidate list during bi-prediction.

181 According to one embodiment of the present disclosure, an image decoding method

performed by a decoding apparatus is provided. The method includes receiving image

information including inter-prediction mode information and inter-prediction type information

through a bitstream; generating a merge candidate list of a current block based on the inter

prediction mode information; selecting one candidate from among the candidates included in

the merge candidate list; deriving an inter-prediction type of the current block as a bi-prediction

based on the inter-prediction type information; deriving motion information on the current

block based on the selected candidate; generating LO prediction samples and L prediction

samples of the current block based on the motion information; and generating prediction

samples of the current block based on the LO prediction samples, the L prediction samples,

and weight information, wherein the weight information is derived based on weight index

information on the selected candidate, in which the candidates include an affine merge

candidate, and the affine merge candidate includes control point motion vectors (CPMV), when

the affine merge candidate includes a CPMV for control point 0 (CPO) positioned at a top-left

of the current block, the weight index information on the affine merge candidate is derived

based on weight index information on a specific block among neighboring blocks of the CPO,

and when the affine merge candidate does not include the CPMV for the CPO positioned at the

top-left of the current block, weight index information on the affine merge candidate is derived

based on weight index information on a specific block among neighboring blocks of control

point 1 (CP1) positioned at a top-right of the current block.

191 According to another embodiment of the present disclosure, an image encoding method performed by an encoding apparatus is provided. The method includes determining

an inter-prediction mode of the current block and generating inter-prediction mode information

indicating the inter-prediction mode; generating a merge candidate list of the current block

based on the inter-prediction mode information; generating selection information indicating

one of candidates included in the merge candidate list; generating inter-prediction type

information indicating an inter-prediction type of the current block as bi-prediction; and

encoding image information including the inter-prediction mode information, the selection

information, and the inter-prediction type information, in which the candidates include an

affine merge candidate, and the affine merge candidate includes control point motion vectors

(CPMV), when the affine merge candidate includes a CPMV for control point 0 (CPO)

positioned at a top-left of the current block, the weight index information on the affine merge

candidate is indicated based on weight index information on a specific block among

neighboring blocks of the CPO, and when the affine merge candidate does not include the

CPMV for the CPO positioned at the top-left of the current block, weight index information on

the affine merge candidate is indicated based on weight index information on a specific block

among neighboring blocks of control point 1 (CP1) positioned at a top-right of the current

block.

[10] According to still another embodiment of the present disclosure, a computer-readable

storage medium storing encoded information causing an image decoding apparatus to perform

an image decoding method is provided. The image decoding method includes receiving

image information including inter-prediction mode information and inter-prediction type

information through a bitstream; generating a merge candidate list of a current block based on

the inter-prediction mode information; selecting one candidate from among the candidates

included in the merge candidate list; deriving an inter-prediction type of the current block as a bi-prediction based on the inter-prediction type information; deriving motion information on the current block based on the selected candidate; generating LO prediction samples and LI prediction samples of the current block based on the motion information; and generating prediction samples of the current block based on the LO prediction samples, the L prediction samples, and weight information, wherein the weight information is derived based on weight index information on the selected candidate, in which the candidates include an affine merge candidate, and the affine merge candidate includes control point motion vectors (CPMV), when the affine merge candidate includes a CPMV for control point 0 (CPO) positioned at a top-left of the current block, the weight index information on the affine merge candidate is derived based on weight index information on a specific block among neighboring blocks of the CPO, and when the affine merge candidate does not include the CPMV for the CPO positioned at the top-left of the current block, weight index information on the affine merge candidate is derived based on weight index information on a specific block among neighboring blocks of control point 1 (CP1) positioned at a top-right of the current block.

[11] According to the present disclosure, it is possible to increase the overall image/video

compression efficiency.

[12] According to the present, it is possible to efficiently construct motion vector candidates

during inter-prediction.

[13] According to the present disclosure, it is possible to efficiently perform weight-based

bi-prediction.

BRIEF DESCRIPTION OF THE DRAWINGS

[14] FIG. 1 is a diagram schematically illustrating an example of a video/image coding

system to which embodiments of the present disclosure may be applied.

[15] FIG. 2 is a diagram schematically illustrating a configuration of a video/image encoding apparatus to which embodiments of the present disclosure may be applied.

[16] FIG. 3 is a diagram schematically illustrating a configuration of a video/image

decoding apparatus to which embodiments of the present disclosure may be applied.

[17] FIG. 4 is a diagram for describing a merge mode in inter-prediction.

[18] FIGS. 5A and 5B are diagram exemplarily illustrating CPMV for affine motion

prediction.

[19] FIG. 6 is a diagram exemplarily illustrating a case in which an affine MVF is

determined in units of subblocks.

[20] FIG. 7 is a diagram for describing an affine merge mode in inter-prediction.

[21] FIG. 8 is a diagram for describing positions of candidates in an affine merge mode.

[22] FIG. 9 is a diagram for describing SbTMVP in inter-prediction.

[23] FIGS. 10 and 11 are diagrams schematically illustrating an example of a video/image

decoding method and related components according to embodiment(s) of the present disclosure.

[24] FIGS. 12 and 13 are diagrams schematically illustrating an example of an image/video

encoding method and related components according to embodiment(s) of the present disclosure.

[25] FIG. 14 is a diagram illustrating an example of a content streaming system to which

embodiments disclosed in the present disclosure may be applied.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[26] The present disclosure may be variously modified and have several exemplary

embodiments. Therefore, specific exemplary embodiments of the present disclosure will be

illustrated in the accompanying drawings and be described in detail. However, this is not

intended to limit the present disclosure to specific embodiments. Terms used in the present

specification are used only in order to describe specific exemplary embodiments rather than

limiting the present disclosure. Singular forms are intended to include plural forms unless the context clearly indicates otherwise. It is to be understood that terms "include", "have", or the like, used in the present specification specify the presence of features, numerals, steps, operations, components, parts, or a combination thereof stated in the present specification, but do not preclude the presence or addition of one or more other features, numerals, steps, operations, components, parts, or a combination thereof.

[27] Meanwhile, each component in the drawings described in the present disclosure is

illustrated independently for convenience of description regarding different characteristic

functions, and does not mean that each component is implemented as separate hardware or

separate software. For example, two or more components among each component may be

combined to form one component, or one component may be divided into a plurality of

components. Embodiments in which each component is integrated and/or separated are also

included in the scope of the present disclosure.

[28] In the present disclosure, "AorB" maymean "onlyA", "onlyB" or "bothAandB".

Inotherwords, "AorB" in the present disclosure maybe interpreted as "Aand/orB". For

example, in the present disclosure, "A, B, or C" means "only A", "only B", "only C", or

"any and any combination of A, B, and C".

[29] A slash (/) or comma (comma) used in the present disclosure may mean 'and/or".

For example, "A/B" may mean "and/or B". Accordingly, "A/B" may mean "only A",

"only B", or "both A and B." For example, "A, B, C" may mean "A, B, orC".

[30] In the present specification, "at least one of A and B" may mean "only A", "only B",

or "both A and B". Further, in the present specification, the expression "at least one of A or B"

or "at least one of A and/or B" may be interpreted the same as "at least one of A and B".

[31] Further, in the present specification, "at least one of A, B and C" may mean "only A",

"only B", "only C", or "any combination of A, B and C". Further, "at least one of A, B or C"

or "at least one of A, B and/or C" may mean "at least one of A, B and C".

[32] Further, the parentheses used in the present specification may mean "for example".

Specifically, in the case that "prediction (intra prediction)" is expressed, it may be indicated

that "intra prediction" is proposed as an example of "prediction". In other words, the term

"prediction" in the present specification is not limited to "intra prediction", and it may be

indicated that "intra prediction" is proposed as an example of "prediction". Further, even in the

case that "prediction (i.e., intra prediction)" is expressed, it may be indicated that "intra

prediction" is proposed as an example of "prediction".

[33] In the present specification, technical features individually explained in one drawing

may be individually implemented, or may be simultaneously implemented.

[34] Hereinafter, embodiments of the present disclosure will be described in detail with

reference to the accompanying drawings. In addition, like reference numerals are used to

indicate like elements throughout the drawings, and the same descriptions on the like elements

may be omitted.

[35] FIG. 1 illustrates an example of a video/image coding system to which the

embodiments of the present disclosure may be applied.

[36] Referring to FIG. 1, a video/image coding system may include a first device (a source

device) and a second device (a reception device). The source device may transmit encoded

video/image information or data to the reception device through a digital storage medium or

network in the form of a file or streaming.

[37] The source device may include a video source, an encoding apparatus, and a transmitter.

The receiving device may include a receiver, a decoding apparatus, and a renderer. The

encoding apparatus may be called a video/image encoding apparatus, and the decoding apparatus may be called a video/image decoding apparatus. The transmitter may be included in the encoding apparatus. The receiver may be included in the decoding apparatus. The renderer may include a display, and the display may be configured as a separate device or an external component.

[38] The video source may acquire video/image through a process of capturing,

synthesizing, or generating the video/image. The video source may include a video/image

capture device and/or a video/image generating device. The video/image capture device may

include, for example, one or more cameras, video/image archives including previously

captured video/images, and the like. The video/image generating device may include, for

example, computers, tablets and smartphones, and may (electronically) generate video/images.

For example, a virtual video/image may be generated through a computer or the like. In this

case, the video/image capturing process may be replaced by a process of generating related

data.

[39] The encoding apparatus may encode input video/image. The encoding apparatus may

perform a series of procedures such as prediction, transform, and quantization for compaction

and coding efficiency. The encoded data (encoded video/image information) may be output in

the form of a bitstream.

[40] The transmitter may transmit the encoded image/image information or data output in

the form of a bitstream to the receiver of the receiving device through a digital storage medium

or a network in the form of a file or streaming. The digital storage medium may include various

storage mediums such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and the like. The

transmitter may include an element for generating a media file through a predetermined file

format and may include an element for transmission through a broadcast/communication

network. The receiver may receive/extract the bitstream and transmit the received bitstream to

the decoding apparatus.

[41] The decoding apparatus may decode the video/image by performing a series of

procedures such as dequantization, inverse transform, and prediction corresponding to the

operation of the encoding apparatus.

[42] The renderer may render the decoded video/image. The rendered video/image may be

displayed through the display.

[43] The present disclosure relates to video/image coding. For example, the

method/embodiment disclosed in the present disclosure may be applied to the methods

disclosed in a verstatile video coding (VVC) standard, an essential video coding (EVC)

standard, an AOMedia Video 1 (AV1) standard, 2nd generation of audio video coding standard

(AVS2), or a next-generation video/image coding standard (ex. H.267 or H.268, etc).

[44] This document suggests various embodiments of video/image coding, and the above

embodiments may also be performed in combination with each other unless otherwise specified.

[45] In this document, a video may refer to a series of images over time. A picture generally

refers to the unit representing one image at a particular time frame, and a slice/tile refers to the

unit constituting a part of the picture in terms of coding. A slice/tile may include one or more

coding tree units (CTUs). One picture may consist of one or more slices/tiles.

[46] A tile is a rectangular region of CTUs within a particular tile column and a particular

tile row in a picture. The tile column is a rectangular region of CTUs having a height equal to

the height of the picture and a width specified by syntax elements in the picture parameter set.

The tile row is a rectangular region of CTUs having a height specified by syntax elements in

the picture parameter set and a width equal to the width of the picture. A tile scan is a specific

sequential ordering of CTUs partitioning a picture in which the CTUs are ordered consecutively

in CTU raster scan in a tile whereas tiles in a picture are ordered consecutively in a raster scan

of the tiles of the picture. A slice may comprise a number of complete tiles or a number of

consecutive CTU rows in one tile of a picture that may be contained in one NAL unit. In this document, tile group and slice can be used interchangeably. For example, in this document, a tile group/tile group header may be referred to as a slice/slice header.

[47] Meanwhile, one picture may be divided into two or more subpictures. The subpicture

may be a rectangular region of one or more slices within a picture.

[48] A pixel or a pel may mean a smallest unit constituting one picture (or image). Also, 'sample' may be used as a term corresponding to a pixel. A sample may generally represent a

pixel or a value of a pixel, and may represent only a pixel/pixel value of a luma component or

only a pixel/pixel value of a chroma component.

[49] A unit may represent a basic unit of image processing. The unit may include at least

one of a specific region of the picture and information related to the region. One unit may

include one luma block and two chroma (ex. cb, cr) blocks. The unit may be used

interchangeably with terms such as block or area in some cases. In a general case, an MxN

block may include samples (or sample arrays) or a set (or array) of transform coefficients of M

columns and N rows. Alternatively, the sample may mean a pixel value in the spatial domain,

and when such a pixel value is transformed to the frequency domain, it may mean a transform

coefficient in the frequency domain.

[50] FIG. 2 is a diagram schematically illustrating the configuration of a video/image

encoding apparatus to which the disclosure of the present document may be applied.

Hereinafter, what is referred to as the video encoding apparatus may include an image encoding

apparatus.

[51] Referring to FIG. 2, the encoding apparatus 200 may include and be configured with

an image partitioner 210, a predictor 220, a residual processor 230, an entropy encoder 240, an

adder 250, a filter 260, and a memory 270. The predictor 220 may include an inter predictor

221 and an intra predictor 222. The residual processor 230 may include a transformer 232, a

quantizer 233, a dequantizer 234, and an inverse transformer 235. The residual processor 230 may further include a subtractor 231. The adder 250 may be called a reconstructor or reconstructed block generator. The image partitioner 210, the predictor 220, the residual processor 230, the entropy encoder 240, the adder 250, and the filter 260, which have been described above, may be configured by one or more hardware components (e.g., encoder chipsets or processors) according to an embodiment. In addition, the memory 270 may include a decoded picture buffer (DPB), and may also be configured by a digital storage medium. The hardware component may further include the memory 270 as an internal/external component.

[52] The image partitioner 210 may split an input image (or, picture, frame) input to the

encoding apparatus 200 into one or more processing units. As an example, the processing unit

may be called a coding unit (CU). In this case, the coding unit may be recursively split

according to a Quad-tree binary-tree ternary-tree (QTBTTT) structure from a coding tree unit

(CTU) or the largest coding unit (LCU). For example, one coding unit may be split into a

plurality of coding units of a deeper depth based on a quad-tree structure, a binary-tree structure,

and/or a ternary-tree structure. In this case, for example, the quad-tree structure is first applied

and the binary-tree structure and/or the ternary-tree structure may be later applied. Alternatively,

the binary-tree structure may also be first applied. A coding procedure according to the present

disclosure may be performed based on a final coding unit which is not split any more. In this

case, based on coding efficiency according to image characteristics or the like, the maximum

coding unit may be directly used as the final coding unit, or as necessary, the coding unit may

be recursively split into coding units of a deeper depth, such that a coding unit having an

optimal size may be used as the final coding unit. Here, the coding procedure may include a

procedure such as prediction, transform, and reconstruction to be described later. As another

example, the processing unit may further include a predictor (PU) or a transform unit (TU). In

this case, each of the predictor and the transform unit may be split or partitioned from the

aforementioned final coding unit. The predictor may be a unit of sample prediction, and the transform unit may be a unit for inducing a transform coefficient and/or a unit for inducing a residual signal from the transform coefficient.

[53] The unit may be interchangeably used with the term such as a block or an area in some

cases. Generally, an MxN block may represent samples composed of M columns and N rows

or a group of transform coefficients. The sample may generally represent a pixel or a value of

the pixel, and may also represent only the pixel/pixel value of a luma component, and also

represent only the pixel/pixel value of a chroma component. The sample may be used as the

term corresponding to a pixel or a pel configuring one picture (or image).

[54] The encoding apparatus 200 may subtract the prediction signal (predicted block,

prediction sample array) output from the inter predictor 221 or the intra predictor 222 from the

input image signal (original block, original sample array) to generate a residual signal (residual

block, residual sample array), and the generated residual signal is transmitted to the transformer

232. In this case, as illustrated, a unit for subtracting the prediction signal (prediction block,

prediction sample array) from an input image signal (original block, original sample array) in

the encoder 200 may be referred to as a subtractor 231. The predictor may perform prediction

on a processing target block (hereinafter, referred to as a current block) and generate a predicted

block including prediction samples for the current block. The predictor may determine

whether intra prediction or inter prediction is applied in units of a current block or CU. The

predictor may generate various information on prediction, such as prediction mode information,

and transmit the generated information to the entropy encoder 240, as is described below in the

description of each prediction mode. The information on prediction may be encoded by the

entropy encoder 240 and output in the form of a bitstream.

[55] The intra predictor 222 may predict a current block with reference to samples within a

current picture. The referenced samples may be located neighboring to the current block, or

may also be located away from the current block according to the prediction mode. The prediction modes in the intra prediction may include a plurality of non-directional modes and a plurality of directional modes. The non-directional mode may include, for example, a DC mode or a planar mode. The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes according to the fine degree of the prediction direction. However, this is illustrative and the directional prediction modes which are more or less than the above number may be used according to the setting. The intra predictor

222 may also determine the prediction mode applied to the current block using the prediction

mode applied to the neighboring block.

[56] The inter predictor 221 may induce a predicted block of the current block based on a

reference block (reference sample array) specified by a motion vector on a reference picture.

At this time, in order to decrease the amount of motion information transmitted in the inter

prediction mode, the motion information may be predicted in units of a block, a sub-block, or

a sample based on the correlation of the motion information between the neighboring block

and the current block. The motion information may include a motion vector and a reference

picture index. The motion information may further include inter prediction direction (LO

prediction, LI prediction, Bi prediction, or the like) information. In the case of the inter

prediction, the neighboring block may include a spatial neighboring block existing within the

current picture and a temporal neighboring block existing in the reference picture. The

reference picture including the reference block and the reference picture including the temporal

neighboring block may also be the same as each other, and may also be different from each

other. The temporal neighboring block may be called the name such as a collocated reference

block, a collocated CU (colCU), or the like, and the reference picture including the temporal

neighboring block may also be called a collocated picture (colPic). For example, the inter

predictor 221 may configure a motion information candidate list based on the neighboring

blocks, and generate information indicating what candidate is used to derive the motion vector and/or the reference picture index of the current block. The inter prediction may be performed based on various prediction modes, and for example, in the case of a skip mode and a merge mode, the inter predictor 221 may use the motion information of the neighboring block as the motion information of the current block. In the case of the skip mode, the residual signal may not be transmitted unlike the merge mode. A motion vector prediction (MVP) mode may indicate the motion vector of the current block by using the motion vector of the neighboring block as a motion vector predictor, and signaling a motion vector difference.

[57] The predictor 220 may generate a prediction signal based on various prediction

methods to be described below. For example, the predictor may apply intra prediction or inter

prediction for prediction of one block and may simultaneously apply intra prediction and inter

prediction. This may be called combined inter and intra prediction (CIIP). In addition, the

predictor may be based on an intra block copy (IBC) prediction mode or based on a palette

mode for prediction of a block. The IBC prediction mode or the palette mode may be used

for image/video coding of content such as games, for example, screen content coding (SCC).

IBC basically performs prediction within the current picture, but may be performed similarly

to inter prediction in that a reference block is derived within the current picture. That is, IBC

may use at least one of the inter prediction techniques described in this document. Thepalette

mode may be viewed as an example of intra coding or intra prediction. When the palette

mode is applied, a sample value in the picture may be signaled based on information on the

palette table and the palette index.

[58] The prediction signal generated by the predictor (including the inter predictor 221

and/or the intra predictor 222) may be used to generate a reconstructed signal or may be used

to generate a residual signal. The transformer 232 may generate transform coefficients by

applying a transform technique to the residual signal. For example, the transform technique

may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a Karhunen-Loeve Transform (KLT), a graph-based transform (GBT), or a conditionally non linear transform (CNT). Here, GBT refers to transformation obtained from a graph when expressing relationship information between pixels in the graph. CNT refers to transformation obtained based on a prediction signal generated using all previously reconstructed pixels. Also, the transformation process may be applied to a block of pixels having the same size as a square or may be applied to a block of a variable size that is not a square.

[59] The quantizer 233 quantizes the transform coefficients and transmits the same to the

entropy encoder 240, and the entropy encoder 240 encodes the quantized signal (information

on the quantized transform coefficients) and outputs the encoded signal as a bitstream.

Information on the quantized transform coefficients may be referred to as residual information.

The quantizer 233 may rearrange the quantized transform coefficients in the block form into a

one-dimensional vector form based on a coefficient scan order and may generate information

on the transform coefficients based on the quantized transform coefficients in the one

dimensional vector form. The entropy encoder 240 may perform various encoding methods

such as, for example, exponential Golomb, context-adaptive rvaiable length coding (CAVLC),

and context-adaptive binary arithmetic coding (CABAC). The entropy encoder 240 may

encode information necessary for video/image reconstruction (e.g., values of syntax elements,

etc.) other than the quantized transform coefficients together or separately. Encoded

information (e.g., encoded video/image information) may be transmitted or stored in units of a

network abstraction layer (NAL) unit in the form of a bitstream. The video/image information

may further include information on various parameter sets, such as an adaptation parameter set

(APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set

(VPS). Also, the video/image information may further include general constraint information.

In this document, information and/or syntax elements transmitted/signaled from the encoding apparatus to the decoding apparatus may be included in video/image information. The video/image information may be encoded through the encoding procedure described above and included in the bitstream. The bitstream may be transmitted through a network or may be stored in a digital storage medium. Here, the network may include a broadcasting network and/or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. A transmitting unit (not shown) and/or a storing unit (not shown) for transmitting or storing a signal output from the entropy encoder 240 may be configured as internal/external elements of the encoding apparatus 200, or the transmitting unit may be included in the entropy encoder 240.

[60] The quantized transform coefficients output from the quantizer 233 may be used to

generate a prediction signal. For example, the residual signal (residual block or residual

samples) may be reconstructed by applying dequantization and inverse transform to the

quantized transform coefficients through the dequantizer 234 and the inverse transform unit

235. The adder 250 may add the reconstructed residual signal to the prediction signal output

from the inter predictor 221 or the intra predictor 222 to generate a reconstructed signal

(reconstructed picture, reconstructed block, reconstructed sample array). When there is no

residual for the processing target block, such as when the skip mode is applied, the predicted

block maybe used as a reconstructed block. The adder 250 maybe referred to as a restoration

unit or a restoration block generator. The generated reconstructed signal maybe used for intra

prediction of a next processing target block in the current picture, or may be used for inter

prediction of the next picture after being filtered as described below.

[61] Meanwhile, luma mapping with chroma scaling (LMCS) may be applied during a

picture encoding and/or reconstruction process.

[62] The filter 260 may improve subjective/objective image quality by applying filtering to

the reconstructed signal. For example, the filter 260 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 270, specifically, in a DPB of the memory 270.

The various filtering methods may include, for example, deblocking filtering, a sample

adaptive offset, an adaptive loop filter, a bilateral filter, and the like. The filter 260 may generate

various kinds of information related to the filtering, and transfer the generated information to

the entropy encoder 240 as described later in the description of each filtering method. The

information related to the filtering may be encoded by the entropy encoder 240 and output in

the form of a bitstream.

[63] The modified reconstructed picture transmitted to the memory 270 may be used as a

reference picture in the inter predictor 221. When the inter prediction is applied through the

encoding apparatus, prediction mismatch between the encoding apparatus 200 and the

decoding apparatus can be avoided and encoding efficiency can be improved.

[64] The DPB of the memory 270 may store the modified reconstructed picture for use as

the reference picture in the inter predictor 221. The memory 270 may store motion information

of a block from which the motion information in the current picture is derived (or encoded)

and/or motion information of blocks in the picture, having already been reconstructed. The

stored motion information may be transferred to the inter predictor 221 to be utilized as motion

information of the spatial neighboring block or motion information of the temporal neighboring

block. The memory 270 may store reconstructed samples of reconstructed blocks in the current

picture, and may transfer the reconstructed samples to the intra predictor 222.

[65] Meanwhile, in this document, at least one of quantization/dequantization and/or

transform/inverse transform may be omitted. When the quantization/dequantization is

omitted, the quantized transform coefficient may be referred to as a transform coefficient.

When the transform/inverse transform is omitted, the transform coefficient may be called a

coefficient or a residual coefficient or may still be called the transform coefficient for uniformity of expression.

[66] Further, in this document, the quantized transform coefficient and the transform

coefficient may be referred to as a transform coefficient and a scaled transform coefficient,

respectively. In this case, the residual information may include information on transform

coefficient(s), and the information on the transform coefficient(s) may be signaled through

residual coding syntax. Transform coefficients may be derived based on the residual

information (or information on the transform coefficient(s)), and scaled transform coefficients

may be derived through inverse transform (scaling) on the transform coefficients. Residual

samples may be derived based on inverse transform (transform) of the scaled transform

coefficients. This may be applied/expressed in other parts of this document as well.

[67] FIG. 3 is a diagram for schematically explaining the configuration of a video/image

decoding apparatus to which the disclosure of the present document may be applied.

[68] Referring to FIG. 3, the decoding apparatus 300 may include and configured with an

entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, a filter 350, and

a memory 360. The predictor 330 may include an intra predictor 331 and an inter predictor 332.

The residual processor 320 may include a dequantizer 321 and an inverse transformer 322. The

entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filter

350, which have been described above, may be configured by one or more hardware

components (e.g., decoder chipsets or processors) according to an embodiment. Further, the

memory 360 may include a decoded picture buffer (DPB), and may be configured by a digital

storage medium. The hardware component may further include the memory 360 as an

internal/external component.

[69] When the bitstream including the video/image information is input, the decoding

apparatus 300 may reconstruct the image in response to a process in which the video/image

information is processed in the encoding apparatus illustrated in FIG. 2. For example, the decoding apparatus 300 may derive the units/blocks based on block split-related information acquired from the bitstream. The decoding apparatus 300 may perform decoding using the processing unit applied to the encoding apparatus. Therefore, the processing unit for the decoding may be, for example, a coding unit, and the coding unit may be split according to the quad-tree structure, the binary-tree structure, and/or the ternary-tree structure from the coding tree unit or the maximum coding unit. One or more transform units may be derived from the coding unit. In addition, the reconstructed image signal decoded and output through the decoding apparatus 300 may be reproduced through a reproducing apparatus.

[70] The decoding apparatus 300 may receive a signal output from the encoding apparatus

of Figure 2 in the form of a bitstream, and the received signal may be decoded through the

entropy decoder 310. For example, the entropy decoder 310 may parse the bitstream to derive

information (e.g., video/image information) necessary for image reconstruction (or picture

reconstruction). The video/image information may further include information on various

parameter sets such as an adaptation parameter set (APS), a picture parameter set (PPS), a

sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image

information may further include general constraint information. The decoding apparatus may

further decode picture based on the information on the parameter set and/or the general

constraint information. Signaled/received information and/or syntax elements described later

in this document may be decoded may decode the decoding procedure and obtained from the

bitstream. For example, the entropy decoder 310 decodes the information in the bitstream

based on a coding method such as exponential Golomb coding, context-adaptive variable

length coding (CAVLC), or context-adaptive arithmetic coding (CABAC), and output syntax

elements required for image reconstruction and quantized values of transform coefficients for

residual. More specifically, the CABAC entropy decoding method may receive a bin

corresponding to each syntax element in the bitstream, determine a context model by using a decoding target syntax element information, decoding information of a decoding target block or information of a symbol/bin decoded in a previous stage, and perform an arithmetic decoding on the bin by predicting a probability of occurrence of a bin according to the determined context model, and generate a symbol corresponding to the value of each syntax element. In this case, the CABAC entropy decoding method may update the context model by using the information of the decoded symbol/bin for a context model of a next symbol/bin after determining the context model. The information related to the prediction among the information decoded by the entropy decoder 310 may be provided to the the predictor (inter predictor 332 and intra predictor 331), and residual values on which the entropy decoding has been performed in the entropy decoder 310, that is, the quantized transform coefficients and related parameter information, may be input to the residual processor 320.

[71] The dequantizer 321 may dequantize the quantized transform coefficients to output the

transform coefficients. The dequantizer 321 may rearrange the quantized transform coefficients

in a two-dimensional block form. In this case, the rearrangement may be performed based on

a coefficient scan order performed by the encoding apparatus. The dequantizer 321 may

perform dequantization for the quantized transform coefficients using a quantization parameter

(e.g., quantization step size information), and acquire the transform coefficients.

[72] The inverse transformer 322 inversely transforms the transform coefficients to acquire

the residual signal (residual block, residual sample array).

[73] The predictor 330 may perform the prediction of the current block, and generate a

predicted block including the prediction samples of the current block. The predictor may

determine whether the intra prediction is applied or the inter prediction is applied to the current

block based on the information about prediction output from the entropy decoder 310, and

determine a specific intra/inter prediction mode.

[74] The predictor 330 may generate a prediction signal based on various prediction methods to be described later. For example, the predictor may apply intra prediction or inter prediction for prediction of one block, and may simultaneously apply intra prediction and inter prediction. This may be called combined inter and intra prediction (CIIP). In addition, the predictor may be based on an intra block copy (IBC) prediction mode or based on a palette mode for prediction of a block. The IBC prediction mode or the palette mode may be used for image/video coding of content such as games, for example, screen content coding (SCC).

IBC may basically perform prediction within the current picture, but may be performed

similarly to inter prediction in that a reference block is derived within the current picture.

That is, IBC may use at least one of the inter prediction techniques described in this document.

The palette mode may be considered as an example of intra coding or intra prediction. When

the palette mode is applied, information on the palette table and the palette index may be

included in the video/image information and signaled.

[75] The intra predictor 3321 may predict the current block by referring to the samples in

the current picture. The referred samples may be located in the neighborhood of the current

block, or may be located apart from the current block according to the prediction mode. In intra

prediction, prediction modes may include a plurality of non-directional modes and a plurality

of directional modes. The intra predictor 331 may determine the prediction mode to be applied

to the current block by using the prediction mode applied to the neighboring block.

[76] The inter predictor 332 may derive a predicted block for the current block based on a

In this case, in order to reduce the amount of motion information being transmitted in the inter

prediction mode, motion information may be predicted in the unit of blocks, subblocks, or

samples based on correlation of motion information between the neighboring block and the

current block. The motion information may include a motion vector and a reference picture

index. The motion information may further include information on inter prediction direction

(LO prediction, LI prediction, Bi prediction, and the like). In case of inter prediction, the

neighboring block may include a spatial neighboring block existing in the current picture and

a temporal neighboring block existing in the reference picture. For example, the inter predictor

332 may construct a motion information candidate list based on neighboring blocks, and derive

a motion vector of the current block and/or a reference picture index based on the received

candidate selection information. Inter prediction may be performed based on various prediction

modes, and the information on the prediction may include information indicating a mode of

inter prediction for the current block.

[77] The adder 340 may generate a reconstructed signal (reconstructed picture,

reconstructed block, or reconstructed sample array) by adding the obtained residual signal to

the prediction signal (predicted block or predicted sample array) output from the predictor

(including inter predictor 332 and/or intra predictor 331). If there is no residual for the

processing target block, such as a case that a skip mode is applied, the predicted block may be

used as the reconstructed block.

[78] The adder 340 may be called a reconstructor or a reconstructed block generator. The

generated reconstructed signal may be used for the intra prediction of a next block to be

processed in the current picture, and as described later, may also be output through filtering or

may also be used for the inter prediction of a next picture.

[79] Meanwhile, a luma mapping with chroma scaling (LMCS) may also be applied in the

picture decoding process.

[80] The filter 350 may improve subjective/objective image quality by applying filtering to

the reconstructed signal. For example, the filter 350 may generate a modified reconstructed

picture by applying various filtering methods to the reconstructed picture, and store the

modified reconstructed picture in the memory 360, specifically, in a DPB of the memory 360.

The various filtering methods may include, for example, deblocking filtering, a sample adaptive offset, an adaptive loop filter, a bilateral filter, and the like.

[81] The (modified) reconstructed picture stored in the DPB of the memory 360 may be

used as a reference picture in the inter predictor 332. The memory 360 may store the motion

information of the block from which the motion information in the current picture is derived

(or decoded) and/or the motion information of the blocks in the picture having already been

reconstructed. The stored motion information may be transferred to the inter predictor 332 so

as to be utilized as the motion information of the spatial neighboring block or the motion

information of the temporal neighboring block. The memory 360 may store reconstructed

samples of reconstructed blocks in the current picture, and transfer the reconstructed samples

to the intra predictor 331.

[82] In this disclosure, the embodiments described in the filter 260, the inter predictor 221,

and the intra predictor 222 of the encoding apparatus 200 may be applied equally or to

correspond to the filter 350, the inter predictor 332, and the intra predictor 331.

[83] Meanwhile, as described above, in performing video coding, prediction is performed

to improve compression efficiency. Through this, a predicted block including prediction

samples for a current block as a block to be coded (i.e., a coding target block) may be generated.

Here, the predicted block includes prediction samples in a spatial domain (or pixel domain).

The predicted block is derived in the same manner in an encoding apparatus and a decoding

apparatus, and the encoding apparatus may signal information (residual information) on

residual between the original block and the predicted block, rather than an original sample

value of an original block, to the decoding apparatus, thereby increasing image coding

efficiency. The decoding apparatus may derive a residual block including residual samples

based on the residual information, add the residual block and the predicted block to generate

reconstructed blocks including reconstructed samples, and generate a reconstructed picture

including the reconstructed blocks.

[84] The residual information may be generated through a transform and quantization

procedure. For example, the encoding apparatus may derive a residual block between the

original block and the predicted block, perform a transform procedure on residual samples

(residual sample array) included in the residual block to derive transform coefficients, perform

a quantization procedure on the transform coefficients to derive quantized transform

coefficients, and signal related residual information to the decoding apparatus (through a bit

stream). Here, the residual information may include value information of the quantized

transform coefficients, location information, a transform technique, a transform kernel, a

quantization parameter, and the like. The decoding apparatus may perform

dequantization/inverse transform procedure based on the residual information and derive

residual samples (or residual blocks). The decoding apparatus may generate a reconstructed

picture based on the predicted block and the residual block. Also, for reference for inter

prediction of a picture afterward, the encoding apparatus may also dequantize/inverse

transform the quantized transform coefficients to derive a residual block and generate a

reconstructed picture based thereon.

[85] FIG. 4 is a diagram for describing a merge mode in inter-prediction.

[86] When the merge mode is applied, motion information on the current prediction block

is not directly transmitted, but the motion information on the current prediction block is derived

using motion information on a neighboring prediction block. Accordingly, the motion

information on the current prediction block may be indicated by transmitting flag information

indicating that the merge mode is used and a merge index indicating which prediction block in

the vicinity is used. The merge mode may be referred to as a regular merge mode. For

example, the merge mode may be applied when a value of a regular mergeflag syntax element

is 1.

[87] In order to perform the merge mode, the encoding apparatus needs to search for a merge candidate block used to derive motion information on the current prediction block. For example, up to five merge candidate blocks may be used, but the embodiment(s) of the present disclosure are not limited thereto. In addition, the maximum number of merge candidate blocks may be transmitted in a slice header or a tile group header, but the embodiment(s) of the present disclosure are not limited thereto. After finding the merge candidate blocks, the encoding apparatus may generate a merge candidate list, and may select a merge candidate block having the smallest cost among the merge candidate blocks as a final merge candidate block.

[88] The present disclosure may provide various embodiments of merge candidate blocks

constituting the merge candidate list.

[89] For example, the merge candidate list may use five merge candidate blocks. For

example, four spatial merge candidates and one temporal merge candidate may be used. As

a specific example, in the case of the spatial merge candidate, blocks illustrated in FIG. 4 may

be used as the spatial merge candidates. Hereinafter, the spatial merge candidate or a spatial

MVP candidate to be described later may be referred to as an SMVP, and the temporal merge

candidate or a temporal MVP candidate to be described later may be referred to as a TMVP.

[90] The merge candidate list for the current block may be constructed, for example, based

on the following procedure.

[91] The encoding apparatus/decoding apparatus may search for spatially neighboring

blocks of the current block and insert the derived spatial merge candidates into the merge

candidate list. For example, the spatial neighboring blocks may include bottom-left corner

neighboring blocks, left neighboring blocks, top-right corner neighboring blocks, top-left

corner neighboring blocks, and top-left corner neighboring blocks of the current block.

However, this is an example, and in addition to the spatial neighboring blocks described above,

additional neighboring blocks such as a right neighboring block, a bottom neighboring block, and a bottom-right neighboring block may be further used as the spatial neighboring blocks.

The coding apparatus may detect available blocks by searching for the spatially neighboring

blocks based on priority, and may derive motion information on the detected blocks as the

spatial merge candidates. For example, the encoding apparatus or the decoding apparatus

may be configured to sequentially search for five blocks illustrated in FIG. 4 in an order such

as Ai - Bi - Bo - Ao- B 2 , and may sequentially index available candidates to constitute

the merge candidate list.

[92] The coding apparatus may search for a temporal neighboring block of the current block

and insert a derived temporal merge candidate into the merge candidate list. The temporal

neighboring block may be positioned at a reference picture that is a different picture from the

current picture in which the current block is positioned. The reference picture in which the

temporal neighboring blocks are positioned may be called a collocated picture or a col picture.

The temporal neighboring blocks may be searched for in the order of the bottom-right corner

neighboring block and the bottom-right center block of the co-located block with respect to the

current block on the col picture. Meanwhile, when motion data compression is applied,

specific motion information may be stored as representative motion information on each

predetermined storage unit in the col picture. In this case, there is no need to store motion

information on all blocks in the predetermined storage unit, and through this, a motion data

compression effect may be obtained. In this case, the predetermined storage unit may be

predetermined as, for example, units of 16x16 samples or units of 8x8 samples, or size

information on the predetermined storage unit may be signaled from the encoding apparatus to

the decoding apparatus. When the motion data compression is applied, the motion

information on the temporally neighboring blocks may be replaced with representative motion

information on the predetermined storage unit in which the temporally neighboring blocks are

positioned. That is, in this case, from an implementation point of view, instead of the predicted block positioned at the coordinates of the temporally neighboring blocks, the temporal merge candidate may be derived based on the motion information on the prediction block covering the arithmetic left shifted position after arithmetic right shift by a certain value based on the coordinates (top-left sample position) of the temporal neighboring block. For example, when the predetermined storage unit is units of 2nx2n samples, if the coordinates of the temporally neighboring blocks are (xTnb, yTnb), the motion information on the prediction block positioned at the corrected position ((xTnb>>n)«n), (yTnb>>n)«n)) may be used for the temporal merge candidate. Specifically, when the predetermined storage unit is units of

16x16 samples, if the coordinates of the temporally neighboring blocks are (xTnb, yTnb), the

motion information on the prediction block positioned at the corrected position

((xTnb>>4)«4), (yTnb>>4)«4)) may be used for the temporal merge candidate.

Alternatively, when the predetermined storage unit is units of 8x8 samples, if the coordinates

of the temporally neighboring blocks are (xTnb, yTnb), the motion information on the

prediction block positioned at the corrected position ((xTnb>>3)«3), (yTnb>>3)<<3)) may

be used for the temporal merge candidate.

[93] The coding apparatus may check whether the number of current merge candidates is

smaller than the number of maximum merge candidates. The maximum number of merge

candidates may be predefined or signaled from the encoding apparatus to the decoding

apparatus. For example, the encoding apparatus may generate and encode information on the

maximum number of merge candidates, and transmit the information to the decoder in the form

of a bitstream. When the maximum number of merge candidates is filled, the subsequent

candidate addition process may not proceed.

[94] As a result of the check, when the number of the current merge candidates is smaller

than the maximum number of merge candidates, the coding apparatus may insert an additional

merge candidate into the merge candidate list. For example, the additional merge candidates may include at least one of a history based merge candidate(s), pair-wise average merge candidate(s), ATMVP, a combined bi-predictive merge candidate (when the slice/tile group type of the current slice/tile group is type B) and/or a zero vector merge candidate which will be described later.

[95] As a result of the check, when the number of the current merge candidates is not

smaller than the maximum number of merge candidates, the coding apparatus may terminate

the construction of the merge candidate list. In this case, the encoding apparatus may select

an optimal merge candidate from among the merge candidates constituting the merge candidate

list based on rate-distortion (RD) cost, and signal selection information indicating the selected

merge candidate (ex. merge index) to the decoding apparatus. The decoding apparatus may

select the optimal merge candidate based on the merge candidate list and the selection

information.

[96] As described above, the motion information on the selected merge candidate may be

used as the motion information on the current block, and prediction samples of the current

block may be derived based on the motion information on the current block. The encoding

apparatus may derive residual samples of the current block based on the prediction samples,

and may signal residual information on the residual samples to the decoding apparatus. As

described above, the decoding apparatus may generate reconstructed samples based on residual

samples derived based on the residual information and the prediction samples, and may

generate a reconstructed picture based thereon.

[97] When the skip mode is applied, the motion information on the current block may be

derived in the same way as when the merge mode is applied. However, when the skip mode

is applied, the residual signal for the corresponding block is omitted, and thus the prediction

samples may be directly used as the reconstructed samples. The skip mode may be applied,

for example, when the value of the cu skipflag syntax element is 1.

[98] Meanwhile, the pair-wise average merge candidate may be referred to as a pair-wise

average candidate or a pair-wise candidate. The pair-wise average candidate(s) may be

generated by averaging pairs of predefined candidates in an existing merge candidate list. In

addition, predefined pairs may be defined as {(0, 1), (0, 2), (1, 2), (0, 3), (1, 3), (2, 3)}. Here,

the numbers may indicate merge indices for the merge candidate list. An averaged motion

vector may be calculated separately for each reference list. For example, when two motion

vectors are available in one list, the two motion vectors may be averaged even if they point to

different reference pictures. For example, when only one motion vector is available, one

motion vector may be used directly. For example, when there are no motion vectors available,

the list may remain invalid.

[99] For example, when the merge candidate list is not full even after pair-wise average

merge candidates are added, that is, when the number of current merge candidates in the merge

candidate list is smaller than the number of maximum merge candidates, a zero vector (zero

MVP) may be inserted last until the maximum merge candidate number appears. That is, a

zero vector may be inserted until the number of current merge candidates in the merge

candidate list becomes the maximum number of merge candidates.

[100] Meanwhile, conventionally, only one motion vector could be used to represent the

motion of a coding block. That is, a translational motion model could be used. However,

although this method may represent an optimal motion in units of blocks, it is not actually an

optimal motion of each sample, and coding efficiency may be increased if an optimal motion

vector may be determined in units of samples. To this end, an affine motion model may be

used. An affine motion prediction method for coding using an affine motion model may be

as follows.

[101] The affine motion prediction method may represent a motion vector in units of each

sample of a block using two, three, or four motion vectors. For example, the affine motion model may represent four types of motion. The affine motion model, which represents three motions (translation, scale, and rotation) among the motions that the affine motion model may represent, may be called a similarity (or simplified) affine motion model. However, the affine motion model is not limited to the above-described motion model.

[102] FIGS. 5A and 5B are diagram exemplarily illustrating CPMV for affine motion

prediction.

[103] The affine motion prediction may determine a motion vector of a sample position

included in a block using two or more control point motion vectors (CPMV). In this case, a

set of motion vectors may be referred to as an affine motion vector field (MVF).

[104] For example, FIG. 5A may show a case in which two CPMVs are used, which maybe

referred to as a 4-parameter affine model. In this case, the motion vector at the (x, y) sample

position may be determined as, for example, Equation (1).

[105] [Equation 1]

mU 1x-mU0 x uo +mvy0 MVx x+ I Y +1 m VOx

tmvymv I YW 1y-mv 0 y mv 1 W-muoyxv0

[106] For example, FIG. 5B may illustrates a case in which three CPMVs are used, which

may be referred to as a 6-parameter affine model. In this case, the motion vector at the (x, y)

sample position may be determined as, for example, Equation (2).

[107] [Equation 2]

fv~-mv 1 x-m 0 x yuox W H

[108] In Equations 1 and 2, {vx, vy} may represent a motion vector at the (x, y) position. In addition, {vO, vyj may indicate the CPMV of a control point (CP) at the top-left corner position of the coding block, and {v1x, vIy} may indicate the CPMV of the CP at the top-right corner position, {v2, v2y} may indicate the CPMV of the CP at the bottom-left corner position.

In addition, W may indicate a width of the current block, and H may indicate a height of the

current block.

[109] FIG. 6 is a diagram exemplarily illustrating a case in which an affine MVF is

determined in units of subblocks.

[110] In the encoding/decoding process, the affine MVF may be determined in units of

samples or in units of subblocks previously defined. For example, when determining in units

of samples, a motion vector may be obtained based on each sample value. Alternatively, for

example, when determining in units of subblocks, the motion vector of the corresponding block

may be obtained based on the sample value of the center of the subblock (that is, the bottom

right of the center, that is, the bottom-right sample among the four samples in the center).

That is, in affine motion prediction, the motion vector of the current block may be derived in

units of samples or subblocks.

[111] In the case of FIG. 6, the affine MVF is determined in a 4x4 subblock unit, but the size

of the subblocks may be variously modified.

[112] That is, when the affine prediction is available, three motion models applicable to the

current block may include a translational motion model, a 4-parameter affine motion model,

and a 6-parameter affine motion model. Here, the translational motion model may represent

a model in which the existing block unit motion vector is used, the 4-parameter affine motion

model may represent a model in which two CPMVs are used, and the 6-parameter affine motion

model may represent a model in which three CPMVs are used.

[113] Meanwhile, the affine motion prediction may include an affine MVP (or affine inter)

mode or an affine merge mode.

[114] FIG. 7 is a diagram for describing an affine merge mode in inter-prediction.

[115] For example, in the affine merge mode, the CPMV may be determined according to

the affine motion model of the neighboring block coded by the affine motion prediction. For

example, neighboring blocks coded as affine motion prediction in search order may be used

for affine merge mode. That is, when at least one of neighboring blocks is coded in the affine

motion prediction, the current block may be coded in the affine merge mode. Here, the fine

merge mode may be called AFMERGE.

[116] When the affine merge mode is applied, the CPMVs of the current block may be

derived using CPMVs of neighboring blocks. In this case, the CPMVs of the neighboring

block may be used as the CPMVs of the current block as they are, and the CPMVs of the

neighboring block may be modified based on the size of the neighboring block and the size of

the current block and used as the CPMVs of the current block.

[117] On the other hand, in the case of the affine merge mode in which the motion vector

(MV) is derived in units of subblocks, it may be called a subblock merge mode, which may be

indicated based on a subblock merge flag (or a mergesubblock flag syntax element).

Alternatively, when the value of the merge-subblock-flag syntax element is 1, it may be

indicated that the subblock merge mode is applied. In this case, an affine merge candidate list

to be described later may be called a subblock merge candidate list. In this case, the subblock

merge candidate list may further include a candidate derived by SbTMVP, which will be

described later. In this case, the candidate derived by the SbTMVP may be used as a candidate

of index 0 of the subblock merge candidate list. In other words, the candidate derived from

the SbTMVP may be positioned before an inherited affine candidate or a constructed affine

candidate to be described later in the subblock merge candidate list.

[118] When the affine merge mode is applied, the affine merge candidate list may be

constructed to derive CPMVs for the current block. For example, the affine merge candidate list may include at least one of the following candidates. 1) An inherited affine merge candidate. 2) Constructed affine merge candidate. 3) Zero motion vector candidate (or zero vector). Here, the inherited affine merge candidate is a candidate derived based on the

CPMVs of the neighboring block when the neighboring block is coded in affine mode, the

constructed affine merge candidate is a candidate derived by constructing the CPMVs based

on the MVs of neighboring blocks of the corresponding CP in units of each CPMV, and the

zero motion vector candidate may indicate a candidate composed of CPMVs whose value is 0.

[119] The affine merge candidate list may be constructed as follows, for example.

[120] There may be up to two inherited affine candidates, and the inherited affine candidates

may be derived from affine motion models of neighboring blocks. Neighboring blocks can

contain one left neighboring block and an upper neighboring block. The candidate blocks

maybe positioned as illustrated in FIG. 4. A scan order for a leftpredictor may beAi -> Ao,

and a scan order forthe upperpredictor maybe Bi-> Bo -> B2 . Only one inherited candidate

from each of the left and top maybe selected. A pruning check may not be performed between

two inherited candidates.

[121] When the neighboring affine block is checked, the control point motion vectors of the

checked block may be used to derive a CPMVP candidate in the affine merge list of the current

block. Here, the neighboring affine block may indicate a block coded in the affine prediction

mode among neighboring blocks of the current block. For example, referring to FIG. 7, when

a bottom-left neighboring block A is coded in the affine prediction mode, motion vectors v2,

v3, and v4 of a top-left (top-left) corner, a top-right corner, and a bottom-left corner of the

neighboring block A may be acquired. When the neighboring block A is coded with a 4

parameter affine motion model, two CPMVs of the current block may be calculated according

tov2andv3. When the neighboring block A is coded with a 6-parameter affine motion model,

two CPMVs of the current block may be calculated according to v2, v3, and v4.

[122] FIG. 8 is a diagram for describing positions of candidates in an affine merge mode.

[123] The constructed affine candidate may mean a candidate constructed by combining

translational motion information around each control point. The motion information on the

control points may be derived from specified spatial and temporal perimeters. CPMVk (k=O,

1, 2, 3) may represent a kth control point.

[124] Referring to FIG. 8, blocks may be checked in the order of B 2 B3 A 2 for CPMVO, and a motion vector of a first available block may be used. For CPMV1, blocks may be

checked according to the order of B1-Bo, and for CPMV2, blocks may be checked according

to the order of A1-Ao. A temporal motion vector predictor (TVMP) may be used with

CPMV3 if available.

[125] After motion vectors of four control points are obtained, the affine merge candidates

may be generated based on the acquired motion information. The combination of the control

point motion vectors may correspond to any one of{CPMVO, CPMV1, CPMV2},{CPMVO,

CPMV1, CPMV3}, {CPMVO, CPMV2, CPMV3}, {CPMV1, CPMV2, CPMV3}, {CPMVO,

CPMV1}, and {CPMVO, CPMV2}.

[126] A combination of three CPMVs may constitute a 6-parameter affine merge candidate,

and a combination of two CPMVs may constitute a 4-parameter affine merge candidate. In

order to avoid the motion scaling process, when the reference indices of the control points are

different, the relevant combinations of the control point motion vectors may be discarded.

[127] FIG. 9 is a diagram for describing SbTMVP in inter-prediction.

[128] Meanwhile, the subblock-based temporal motion vector prediction (SbTMVP) method

may also be used. For example, the SbTMVP may be called advanced temporal motion vector

prediction (ATMVP). The SbTMVP may use a motion field in a collocated picture to improve

motion vector prediction and merge mode for CUs in the current picture. Here, the collocated

picture may be called a col picture.

[129] For example, the SbTMVP may predict motion at a subblock (or sub-CU) level. In

addition, the SbTMVP may apply a motion shift before fetching the temporal motion

information from the col picture. Here, the motion shift may be acquired from a motion

vector of one of spatially neighboring blocks of the current block.

[130] The SbTMVP may predict the motion vector of a subblock (or sub-CU) in the current

block (or CU) according to two steps.

[131] In the first step, the spatially neighboring blocks may be tested according to the order

ofAi,B1,BoandAoinFIG.4. A first spatial neighboring block having a motion vector using

a col picture as its reference picture may be checked, and the motion vector may be selected as

a motion shift to be applied. When such a motion is not checked from spatially neighboring

blocks, the motion shift may be set to (0, 0).

[132] In the second step, the motion shift checked in the first step may be applied to obtain

sub-block level motion information (motion vector and reference indices) from the col picture.

For example, the motion shift may be added to the coordinates of the current block. For

example, the motion shift may be set to the motion of Ai of FIG. 4. In this case, for each

subblock, the motion information on a corresponding block in the col picture may be used to

derive the motion information on the subblock. The temporal motion scaling may be applied

to align reference pictures of temporal motion vectors with reference pictures of the current

block.

[133] The combined subblock-based merge list including both the SbTVMP candidates and

the affine merge candidates may be used for signaling of the affine merge mode. Here, the

affine merge mode may be referred to as a subblock-based merge mode. The SbTVMP mode

may be available or unavailable according to a flag included in a sequence parameter set (SPS).

When the SbTMVP mode is available, the SbTMVP predictor may be added as the first entry

of the list of subblock-based merge candidates, and the affine merge candidates may follow.

The maximum allowable size of the affine merge candidate list may be five.

[134] The size of the sub-CU (or subblock) used in the SbTMVP may be fixed to 8x8, and

as in the affine merge mode, the SbTMVP mode may be applied only to blocks having both a

width and a height of 8 or more. The encoding logic of the additional SbTMVP merge

candidate may be the same as that of other merge candidates. That is, for each CU in the P or

B slice, an RD check using an additional rate-distortion (RD) cost may be performed to

determine whether to use the SbTMVP candidate.

[135] Meanwhile, the predicted block for the current block may be derived based on the

motion information derived according to the prediction mode. The predicted block may

include prediction samples (prediction sample array) of the current block. When the motion

vector of the current block indicates a fractional sample unit, an interpolation procedure may

be performed. Through this, the prediction samples of the current block may be derived based

on the fractional sample unit reference samples in the reference picture. When the affine

inter-prediction (affine prediction mode) is applied to the current block, the prediction samples

may be generated based on a sample/subblock unit MV. When the bi-prediction is applied,

the prediction samples may be used as the prediction samples of the current block derived

through a weighted sum or weighted average (according to a phase) of the prediction samples

derived based on the LO prediction (ie, prediction using the reference picture and MVLO in the

reference picture list LO) and the prediction samples derived based on the LI prediction (ie,

prediction using the reference picture and MVLi in the reference picture list LI). Here, the

motion vector in the LO direction may be referred to as an LO motion vector or MVLO, and the

motion vector in the LI direction maybe referred to as an LI motion vector or MVL1. Inthe

case where the bi-prediction is applied, when the reference picture used for the LO prediction

and the reference picture used for the L prediction are positioned in different temporal

directions with respect to the current picture (that is, case corresponding to the bidirectional direction or bi-prediction), which may be called a true bi-prediction.

[136] Also, as described above, reconstructed samples and reconstructed pictures may be

generated based on the derived prediction samples, and then procedures such as in-loop

filtering may be performed.

[137] Meanwhile, when the bi-prediction is applied to the current block, the prediction

samples may be derived based on a weighted average. For example, the bi-prediction using

the weighted average may be called bi-prediction with CU-level weight (BCW), bi-prediction

with weighted Average (BWA), or weighted averaging bi-prediction.

[138] Conventionally, the bi-prediction signal (ie, bi-prediction samples) may be derived

through a simple average of the LO prediction signal (LO prediction samples) and the LI

prediction signals. That is, the bi-prediction samples are derived as an average of the LO

prediction samples based on the LO reference picture and MVLO and the L prediction samples

based on the L reference picture and MVL1. However, when the bi-prediction is applied,

the bi-prediction signal (bi-prediction samples) may be derived through the weighted average

of the LO prediction signal and the LI prediction signal as follows. For example, the bi

prediction signals (bi-prediction samples) may be derived as in Equation 3.

[139] [Equation 3]

Phibpred = ((8- *Po+w*P +4»3

[140] In Equation 3, Pbi-pred may indicate a value of a bi-prediction signal, that is, a

prediction sample value derived by applying bi-prediction, and w may indicate a weight. In

addition, PO may indicate the value of the LO prediction signal, that is, the prediction sample

value derived by applying the LO prediction, and P1 may indicate the value of the L prediction

signal, ie, the prediction sample value derived by applying the L prediction.

[141] For example, 5 weights may be allowed in the weighted average bi-prediction. For

example, the five weights w may include -2, 3, 4, 5, or 10. That is, the weight w may be

determined as one of weight candidates including -2, 3, 4, 5, or 10. ForeachCUtowhichthe

bi-prediction is applied, the weight w may be determined by one of two methods. In the first

method, the weight index may be signaled after a motion vector difference for an unmerged

CU. In the second method, a weight index for a merged CU maybe inferred from neighboring

blocks based on a merge candidate index.

[142] For example, the weighted average bi-prediction may be applied to a CU having 256

or more luma samples. That is, when the product of the width and height of the CU is greater

than or equal to 256, the weighted average bi-prediction maybe applied. Inthe case of alow

delay (low-delay) picture, five weights may be used, and in the case of a non-low-delay picture,

three weights may be used. For example, the three weights may include 3, 4 or 5.

[143] For example, in the encoding apparatus, a fast search algorithm may be applied to find

a weight index without significantly increasing the complexity of the encoding apparatus.

This algorithm may be summarized as follows. For example, when the current picture is a

low-delay picture when combined with adaptive motion vector resolution (AMVR) (when

AMVR is used as inter-prediction mode), unequal weights may be conditionally checked for

1-pel and 4-pel motion vector precision. For example, when combined with affine (when the

affine prediction mode is used as the inter-prediction mode), in the case where the affine

prediction mode is currently selected as the best mode, the affine motion estimation (ME) may

be performed on unequal weights. For example, when two reference pictures of bi-prediction

are the same, unequal weights may be conditionally checked. For example, when a specific

condition is satisfied depending on a POC distance between the current picture and a reference

picture, a coding quantization parameter (QP), and a temporal level, unequal weights may not

be searched.

[144] For example, the BCW weight index may be coded using one context coded bin

followed by a bypass coded bin. The first context coded bin may indicate whether the same

weight is used. When the unequal weights are used based on the first context coded bin,

additional bins may be signaled using bypass coding to indicate unequal weights to be used.

[145] Meanwhile, when the bi-prediction is applied, weight information used to generate

prediction samples may be derived based on weight index information on a candidate selected

from among candidates included in the merge candidate list.

[146] According to an embodiment of the present disclosure, when constructing a motion

vector candidate for a merge mode, weight index information on a temporal motion vector

candidate may be derived as follows. For example, when a temporal motion vector candidate

uses bi-prediction, weight index information on a weighted average may be derived. That is,

when the inter-prediction type is bi-prediction, weight index information (or a temporal motion

vector candidate) on a temporal merge candidate in the merge candidate list may be derived.

[147] For example, weight index information on a weighted average with respect to a

temporal motion vector candidate may always be derived as 0. Here, the weight index

information on 0 may mean that the weights of each reference direction (ie, the LO prediction

direction and the LI prediction direction in bi-prediction) are the same. For example, a

procedure for deriving a motion vector of a luma component for the merge mode may be shown

in Table 1 below.

[148] [Table 1]

&4.2.2Derivation process for ma motion vectorsfor merge mode

This process is only invoked when merge flag[ xC][ yPb ]is equal to 1,where (xCb yChb)specify the top left sarnple of thecurrentlumascoding block relatives the topleft luma sample of the current picture. Inputs to this process are: - alumalocaton(xCyCb)of top-left p ofthecurrentmacodingblock relative tothe top left luma sample of th current picture

- a variablech~idt specifyin the width of the current coding blockinI ua sap1e, - a variablecebHeigh specifinghe height ofthe current coig blockin uassaples Outputsofthisprocessare:

- the luma motionvectors inl/16 fractional-sample accuracytnvLo[ 0][ 01]and mvLl[ 011[0], - the reference indices refldx and refldx - the prediction list utilization flags predFlagL0[ 0]and pred~lagLiE101.0] - thei-prediction weight index gildx

The i-prediction weight indexgbidxissetequalto. Themrotion vectors mvLO 0][ 0] andmnwL1[ 011[0],the reference indices refldxLf and reftdxL1land the prediction utilization flags predFagLO|[ 01[0]and predFlagL1[10I][01]are derived by the following ordered steps: L. The derivation processformegngcandidatesron: neighbouring codigtnts asspecifiedin clau s48 ;3is ivokedwith the lumacodnmgblocklocation ixChbyCh), the luma cding block widthcebWidth and thehiuma coding block height ehHeight as inputs and the output bengthe availability flags avadlableFlagAo avsalableFlagAi, avadlableFlagBe avadlableFlagBs and avcailableFlag3y te referenceindices refldxLXAs retdxLXA; rftdxXiB rfidxLXB: and refmtxXB thepprdctronlhstutilbzation flagsprdla XNs predlagUXA prdIa TX!Bs prdIagtXB: asndprdlgXB: and tomononvectors mLX mrmvXAt mLXBR mLXB: ibnxt admvLXB,.wittidxB X bein,0or ndthhi-:pediction weightindices gbtdxAt bidx ,gbddxs,

2. Tlhe referenceindice,refidxL XCol with XheiesU01,and thei-pedictionwneightndx gbd ol for the ttmporalt ingm candidateCola:reset equal to0u

3I The dervaion process for temporal lunmaotiovector prediction asspeciiedmmiauseS4'11 isinvoked with the lualocation (xCb. yCb,the lumacodngblock widthbWidth. theurnascoding block heightcebHeigh and the variable refldxL0Col as inputs and the output bengtheaalabiity flag avaidableFlagLoCol and the temporal motionvectorsmvLoCoblThe variables availableFlageol, pred2 agL1Col andpredlag lcolarederied asfollows:

avadlableFlaotol availableFlagLOCol (8-283)

pred~lagbtcol=maaiablef-lagLacol (8-284)

predlagLlColE= 0 (8-285)

gbildxCol=0 4, Mt xTxi 4. \\hen goup -d ie equalt o B the dervation pre for tempe ailuamotionvss s d~on ecr asspciiedin1clause8A.2A I1 invokedw ithl insl3cIat~aion-x b i hlumcdlock xvidthcbWidh th-eluma codingblock heihtcbHe yht nd th aialerefldxt Kolasinpus ad theoutnput beingthe aalailtyflaaailbe-lagL iCol ad there emoal motionviec tormv LlCol Thearables nabbef lagcoand predE leag~oaredem-edasfolows

availableFlagCol= available~lagLOCol ||availableFlagLlCol (8-286)

[1491 predFlagLiCol = availableFlag ICol (8-287)

5.Themergin cadidat litmergeCandList, is constructed asfolows:

i a aleFlagA mergeCandListi-H-=Ai ifi asaableFlagB) mergeCandListi--=B 1 ti availableFlagBs me-geCandLiti-- = (8-288) i avaiiable~laeAs) mergeCandListti-H-=A, ffav aiableFlagB: i mnergeCandtst[ie--=B2

iti m~~a~nig Col t ma geCandLisr[ H-]) Col

6. The variable nu1CurrMergeCadand numOigMergeCandare set equal to the number of merging candidates the mergeCansdList. S hennumCrMege disless han(M Mrg d - 1) and N andis greater than 0,thefolowingapplies:

- The derivation processof lutoir-hasdinerimg anidtoaspecn6 m 84 26 isuroked mt mergCandLis and numsCurrMergeCand at inputs and modified muergeCandList and mCur gCadnad out

- mnunigMerget andissetequalto nunC unrMegCand 8sThe denvtion proes forparuisea:netage mergingcandidaee peifled in clause85A4 isinvouked wit mergeCandtat the referenceindices refidLON ad refidxLN the predictionlist utiization figs predFlagLQN and predFlagLIN. the motion -ectorsnmvLON dandvLIN ofevrmcandidateN nmerg ~ndL'st numnCurMergeCand ado nu igMergeCand asinp:uts ad te cttisaigned so mergeCand i u.umCurrMergeCani she rfre ides reftdxLa- adi and re fldxL 1avgC ands the predi:ctionlist utilization flags predrlagLoDargCandsand predlagLavgCand nd the motion vectors mvi.0aveCanda andimvL 1avgCnda .ofevery newccdidateaogandb eng addedio mergeCand it.Thehi-prediction weightindexgb'dx of erynew candidate avgCand 5 bing added into mergeCadList isset equal to0.The nuber of caddate bem added, num 'gMereCand us set equal to ( nun urMerg~ad - naOngergeCand) Then numrMrgeCan i geater thano0.k ranges fromo0tonnm gMergCand-li nlou

[1501 9. Thedriatonprocee forz romotion to meg adies pecified inclauae84.2.5is ivoked with the mergeCandL&th reference indices refldstllNand refldxL1N. the predictionlist uibt' on lgs pred ~L- 0N and pred lagLIN, the motionvectorsimvLON and mvL1N of every A N meeC adnu It M geCandasiputs and the outputisassignedto mergeaandList numCrMergeCand. the reference indices refldxL~zsroCandm and reftrL ~ioCnm th ped' cton ht utilization flags predFlagL.07erorande and pedI lazroCandm nd the motion-ectorsumsLzeroCandanardmvtLIzroCandm of every new candidatezeroCad being addedmiomergeandist.Thehi:-prediction weight index gbidx of every new canidt zroand inm addedimnomer CandL ist is set equal to 0.The number ofcandidates being added. susmZeroMergeCand is set equal to (insimCurrMeroeCand - numifrostergeCand -ozmnAveergefandI/Whenminm7ernierefandis greterha0.iragesfrom ato num/erwrpemd- -1, inclusive. 10. The variable mergeldx~ffset is set equal to0. 11. Wen -md_flag[ xCh[ yCbh]isequal toI1,thevariablesinvdCntis set equal to 0and tThe following applies until mmvdCntis getr than (mergeidx[ xCb ][yChI}+mergeldxffset )or ntisequaltoM mMergeCand: - When anidate megCandLit|[ mmdCnt ]uses the current decode picture a its reference pictur, mereldOffset' i inremented by1.

[151] - The ariable meeented by1 -adCtin

12. The following ssgmments are made with N heing the candidate at poaitn merge nd~~ yCh]i -tmegeldxOffset in the meinmg caniae list mergelandLiat iN - ierge(andList mege:d\x\xh]j[y] snhj ergeld\offse j)anid Nbeingreplaced byfOor1:

refdxLX refldxLXN (8-289)

predFlagLX[ 0][0]predFlagLXN (8-290)

mvLX[0 ][ 0][ 0 -mvLXN[ 0] (8-291)

mvLX[ 0 ][0 ][1 ]= mvLXN[ 1] (8-292)

gbi1dx- ghildxN (8-293)

13. When nmvdflag[ Cb.][yCisequal to1, thefollowingapplies: - TheIvainrc regmtovcodfeecaseifid in827isnoedwihh lmalocation i xhtb :b)the lumnamotionvetrs mvxI[ 0][i0], mvt[ 0][0].jtheeeene indices :eIldxL . refldxE and the prediction lit utizatn flags predFlagf 0][0] and predflagk1[00]ajsnpus nd the motonectodierences mit dL and m~vh asoutmpts -Thlemotionv\et ord!ifene ml\dl ia dded tothbemer ge moionv0\etorsm\vIforXbheng al.nd I as follows: mvLXL[0[ 0] v]= mMvdLX[ 0] (8-294)

mevLX[ 0][ 0][I1]+= mMvdLX[ 1] (8-295)

[1521 11531 Referring to Table 1, gbildx may indicate abi-prediction weight index, and gbidxCol

may indicate abi-prediction weight index for atemporal merge candidate (eg, atemporal

motion vector candidate in the merge candidate list). In the procedure for deriving the motion

vector of the luma component for the merge mode (Table of Contents 3of 8.4.2.2), the

gbildxCol may be derived as 0. That is, the weight index ofthe temporal motion vector

candidate may be derived as 0.

[154] Alternatively, aweight index for aweighted average of temporal motion vector

candidates may be derived based on weight index information on acollocated block. Here,

the collocated block may be referred toas acol block, aco-located block, or aco-located

reference block, and the col block may indicate ablock at the same position as the current block

on the reference picture. For example, aprocedure for deriving amotion vector of aluma

component for the merge mode may be asshown in Table 2below.

[155] [Table 2]

8..2 De itionprocess for luma motion vetrs formerger ode

Thi proes only invoked when merge flag[ C ][ yPb is equal to1, where ( xCb, b ) pecif tIetop leftsample of the current luma codIg block relative to the top-leftI pe of the uent picture

Inputsto thisprocess are: -a lmnlocation (xCb, yCb )of the top-Ief sample of te current lumacoding block relative to the top leftluma sample of thcurrenpicture, - avariable ebWidth specifying the width of the current coding block in luma saples - avariablecebHeight specifying the height of the current coding block in luma saples

Outputsofthisprocess'are: - the luma motion vectors in 1/16 fractional-sample accuracy mvL[0 [ 01]and mvLl1[ 01][01] - the reference indices re£[dxLo and refldxLI -the prediction list utilization fags predFlagL|[ 01][0] and predolagLi101

, - thehbi-prediction weight index gbildx_ The bi-prediction weight index gbidx is set equal to 0. The motion vectors mvLO[0[ 010andinvLl[01][01], the reference indices refidxL0nd refdx 1 dthe predictionutiilization ags predFlgL00 ]]and pred~lagLI[ 011[0]are derivdby tefollowing ordel steps: I The derivationprocessfor mergingccadidate from neighbourmg odm amt a pcifiedin clause864.23 isinvokedwith the luma codngblock location (txCb,yCb Ete luma coding block width cbWidth and the luma codingblock heiob ehight asinputs, ad teotput bgm he aadabdiy fSag availablelaAe, a-eilsablagA aa1bllaB1> aadbleFlaB: and a-allableFlagB 2 ,the reference indicesrefidxX refIdxXM refdxLXB relidxLXB ad re~xfL , phprdiction litutizeton fags predIa L ppdFlu LXAi prelaL s predIa XB: adpp 1d aXB2 ad temotonv ecs mLXAe mvLXAisenwLXBe nvLXB: ndmunLXBmvih Xbeing 0orl1.andtheipred:tin uitieght e gb ,~ bddxA gbildxB gbildxfli gbudxB: 2. The refernemdice refldx XCo.wihX bimng0orI2.and thehi-predictioni inde gbildxCol for the tmporan mging cadidate Col are set equal to0.

3. Thederivationprocessfor temporalluma motionvetr pr2eiton asspecifedinimnclase8A1I sin!voked withthlelia location (t .hUyb.theina cdngblockwhidthc b~idth.thie codng bloc:kheihtcbHesgr and thevaribe refdxIColainputs and theotputbengtheavaadity Sag avaiabheilagLOCol andlthe temporal moineteormvL0Col.TheariablesvailableFlaCol predFlegLo andmlpred~agLI Col are demved as follows availableFlagCol= availableFlagLOCol (8-283)

predFlagLoCol = availableFlagLOfol (8-284)

pred~lagL!iCol=0 (8-285)

4 Whaenb:grotutpise aqu oton pndiction toB, te dem'aonprocesstemporal lr ete asspecifiedimnclause8a4.2.1ii nvokedwaith theluma location ixab yfh),the lmacodingblock Sdn ebmih 1hluacoding block ight eblesht adthe i ablereffdxa~lsin puts ad heoutput bimng a-albduttlag ailbl lagLIo K 1ad t:poalmtonvecorlovIs Col ITheviaales avadableilagiolend pre:d~ao1Coar e derivedafollows

avaihdbe lag ol a a ble HagL olI availble la4.lal (8-286)

[1561 predFlagLlCol= availableFlagLlICol (8-287) gbildxCol= ghildxCol (x-xxx)

5.The mergingcandidaet mergCsndLut isnstructedasfollows

i=0 it~ilaubleFlagd

) merger andList[i+e--] Ai ifi avaalabl-FlagB 1

) meraeCandL[ eiqua =B if avalableFlagBni mnereCandLis[i+--]=Be (8-288 iii availableFlagAiji merge an sti+--]=A5

me gaandL iiiav ailablehlagt o1) merg etand Lsst[s+ ]= Col

6. The variablesnuCurMergeCand ad numOrig ergeCand are senqal tothe number of merging, candidaesinthemergeCandLit. 7. Whn nuCurrMeread is lssha (MaxNumMergead -1) adNuraHmvpCand isgreater thn0, the fo~owing applies - The deivation pocess of hsor-basedinergin candidae asaspecfed in8.416 iinvoked with mergeCandList, and numCurrdergeCand as inputs, and modified mergeCandLst and numCurrMereCand as outputs

isset equal to numCurrMergeCand.

[1571[157] -numOrigMergeCand

8 average merging candidates specifiedin clause 8 4 The derivation processforpairwise 4is invoked wit geandLitt ferenceindicesrefldxON adre IN t pdio it utilzaon flagspredFl ON nd predFlagilN 'he motionvectora m'tN ndmnIN of eer ra~dat N imergetand st nuCurMergeC and and nunsOngergeC anmputs n theoouttis sgnd to mergeCan 1a. numeurrMergeland, the refernc indice refidxt0avgCand and retidxL 1avgC d thsepredictionlitutibzationflagspredFlagLOavgCandandpe pe gt aCandi anidthe mononv ctors mvLugCandi and mvt ingCands of every new cadi s a-gCand being adddsinto mergCandi LThe bi-predictinnweightddxgbildx ofeer new cadidate avrad bein addeditomerg CandL istiset eual oO.The numbr of canddatesomadded, numrgMergeand( is set equal to (numCurrMereCad On rgCandI When numvgMergeCand is greater thanO0.kLranges from 0eonnu~ ergeCaud- 1inc luwv 9.The derivation processfor zero motion vector mergig cmd et speiiedimnclue8AS 4 is linked with themergeCandList.the referenceindice rCtL-D andr re i1N. te preditnniht utihization flags predFlayLON and predFlsgLIN, hemotionvsectorsimnLON ad mL1N of every candidate Nii mreCand iad nuCurrMergeCand asimputs and the output isgped to mergeCndLis. numCurMeConi the reference indices refddxL0er ~ns and reIdx 1eroCad the pedienon hist tilization flag predFlagLOaeroCand, ad pred~gLteroCm and dthei mtion vetorimvOzeroCand, andimntlzeroCandm of everyone candidainerCnd bimn addedinto mer8 adsat Thehbiprediction weightindex gbiidx ofevery newcanchae zeroCandi nem addediomergeCand~tis aset equal to0. The number of canddates being added, nmnsZeroMergeCand. s set equal to nnCorMergeCand nunOrig~rCand nums AlorgeC and)iWhen numoeroMergeCandis gater tan anmge fi n toninumZeetreCand - 1inclusive. 10. The iaribl mereldxOffset isset equal toO0 ItL Wen mmd_la[ ixCh] Cb ]is equal toti h Iusbl umdCtissset equal toeand i~he followmogapplies unt m lCuts aratrihn rim eidx Cb]['C b ]+mregeldsOffst :o

[158] nnvd nuao axNMe nd: n d mrecan I a mIvdCt ] the current picture ,oded as its picture mariTaxOffeset mramented hv

- Thx 1abi-lnacx JCt - renmen d - 1

. 12. The feooinmg assgnments are made with N bemng the candidate at position mtergeidx[ xCb ][ygCb ]-tmergeldx0ffe in the :erging candidate his mergeCandLis ( N -mergeCandListimerge id8 Cb]{ Cb ]+ mergeldxofnset]}) and Xbenerepaced by0or1: refldxLX =reftLXN (8-289)

predFlagLX[0][0]=predi-lagUx (8-290)

mvLX[ 0][ 0][ 0]=nivLXN[ 0] (8-291)

mvLX[ ][ []= mvLXN[1] (8-292)

gbildas bidxN (8-293)

13 When m1 dflA[ x ][ : iequal I thetsfolwnapple - The derivation processfor mergemotionviector differ eceasspecifiedin8A2 asinvtre dwiith thelunalocation x(b Cbt am motonvetrs mvL[[]0mvLl[0J[O]jthe referenceindices rlaidt, ref1 1 ad the predictionistutlhzationftlagspredlagL0[ 0][0"] andppidl[0U][ 0] aioput and the moionvectordifference 0~ JLJn mMidL1as

- The motion 1etodtfferenc~ mmd Xinaddd to the mergmoion i ctoi mi LX forXbeing 0 ad1 asfollws mvLX[0 ][ 0][ 0]+= mMvdLX[ 0] (8-2 4):

mvLX[ 0 ]j0][ 1]+i= mMvdLX I] (8-295)

[1591

[160] Referring to Table 2, gbildx may indicate abi-prediction weight index, and gbidxCol

motion vector candidate in the merge candidate list). In the procedure of deriving the motion

vector of the luma component for the merge mode, when the slice type or the tile group type is

B (Table of Contents 4of 8.4.2.2), the gbidxCol may be derived as gbidxCol. That is, the

weight index of the temporal motion vector candidate may be derived as the weight index of

the col block.

[161] Meanwhile, according toanother embodiment of the present disclosure, when

constructing amotion vector candidate for amerge mode in units of subblocks, aweight index

for aweighted average of temporal motion vector candidates may be derived. Here, the merge

mode in units of subblocks may be referred toas anaffine merge mode (in units ofsubblocks).

The temporal motion vector candidate may indicate asubblock-based temporal motion vector candidate, and may be referred to as an SbTMVP (or ATMVP) candidate. That is, when the inter-prediction type is bi-prediction, the weight index information on the SbTMVP candidate

(or a subblock-based temporal motion vector candidate) in the affine merge candidate list or

the subblock merge candidate list may be derived.

[162] For example, the weight index information on the weighted average of subblock-based

temporal motion vector candidates may always be derived as 0. Here, the weight index

information of 0 may mean that the weights of each reference direction (ie, the LO prediction

procedure for deriving a motion vector and a reference index in a subblock merge mode and a

procedure for deriving a subblock-based temporal merge candidate may be as shown in Tables

3 and 4 be

[163] [Table 3]

8AA..2 Derivationprocess for motion vectors and reference indices in subblock merge I de Inputsothisprocessare: - aluaslocation(aC, yb)ofthe toplefisample ofthecurrentuma coingblock lta tot:he top lefttluina sapeof te currentpcue, - twoa vaiblescbWidt adebHight secifing the width andthe height of te luma coding block Outputsof thisprocess are: - the number of luma coding subblocks in horizontal directions uSbX andin vertical direction numnSbY, - the referenceindicesrefdxLOandrefdxL ; - the prediction list utilization flag arrays predtFlagLt[xSbldx][ySbIdx] and predlag[ xSbldx]LySbldx], - thelumna subblock motion vector arrays in i156fractional-saraple accuracy mvLO[ xSbldx][ ySbidx ]and mvL1[ xSbldx]|[ ySbldx ]withSbidx = 0numnSbX - 1,ySblidx= -nunSbY-~ 1, - the chroma subblock motion vector arrays in 1/32 fractional-sample accuracysnvCLO[ xSbldx]|[ ySbdx ] and mvCL1[ xsbldx ][ ySbdx ]withxsbIdx = .numiSbX - 1, ySbIdtx = nuShY -31, - thehbi-prediction weight index gbilda. The variables numSbX numnSbYand the subbock merging candidate list subblockiergeCandList are derived by thefollowingorderit p 1. When spssmvpenabledflag is equal o 1the following applies: lTe decriv:aipocessIforanrl i didt 5sfUr ' sgbuil coding U~i 1 asspc in-' g11 clause8.4.2.3isinvok waaIit 1l l~a codinloklocat-.inl b (_b). Inmacollingul boidth cibidth the Im oding blockhesh c~Inght ud thluina.odingblock w dth asinputs and heoutputbeng te vilb asailabFla alableFlaA sablFla, Esa :da aulbIF aB. heeifrnce inca refidxX cubElagB

:eldxtXXi li LXBi rfidaLXD. ad tefdi Xt epredition it unizan flag pedlalX prd laLtXA preith LXEBpred laLXB: itdprefa LXEB ad the motionve ctorsemvLXAs mnL-XAj m\ LXE . DiXE.an itXE.wthnXbelingd or

- Thedervatonproces for ubblok- bad temporal mer ,candidates as specific clause8.4.43isimnoked with theI ua location ( Cb. yCb )the luacodingblokwith cbWith he lua codmn block height ebHeight, the avalabihi flags avaiable laA availableFlagfti avala1lFa,E availableFlagBi, the reference minces edxLXA refldxLXAi re lxX~s re lxXE 1 the predictionlisttiuihanion fla, iteFlayLXAs, pred lgLXA: prdlagLX~se prdlagLXBi and shenoton ector inLXA0 in'LXA:, mnvLX~s mnLXB: as puts itdthe outputbemg te avadabhe flag axaiableFlaySbCol the b it eition~ w in mdxgbIldSbCol the nubrof luma :odingsubbloksi horizontal diretionnnuSbX andinxvrticaldiecton numSbY. he reference inices reftdxSbCol. the Imoionu ectors mv LXSbCol[ xSbidx HySbidx t dtepedictionslisutilzationflags pred lgLXSbCo[ xSbldx]yVSbldx ] with NSbd = nnuSbX - 1, vSbhd = 0 .umSbY -lIand Xbemngllorl1 2. When p-affmeeabledt_fla_ a equa 1eI h aple location s t NbA -NbAi b A. NbAi:, <xaba. uNbA(. ixD saybB i (aNDb, ybBi ). (xDB. yObB.) E GBviNbB) adlte asables numSbX ad nuSbY t deri fda ollows: ( xAsyA ) = ( xCb - 1, yCb +cbHeight ) (8-536) ( xAi yAi ) =(xC'b-, yCb +-cbHeight-I1) (8-537) ( xA2 ,yA 2 )= ( Cb - 1, yCb ) (8-538) ( xBsyloi)= (xCb+cebWidth ,yChb- 1) (8-539) ( xi yB1i)= ( aCb+cebWidth - 1, yCb - 1 ) (8-540) ( xBs yB )= (xCh- 1, yCb- 1 ) (8-541)

[1641 (xByyB)=(xC, yChl-) (8-542) numiSbX~c bit»2 (854) umSbY= c ght (8-54) 3. Wnsp a i n dflage l to1. t nabl asiabl stequaltoFALSE and the followingapplhesbfri xNbAa yNbAs) from ixNbAs i NbA:, to -xNbAi y3bA:) -. Theavailabilhtyderiatonprocesfor ablock as specifiedimneisuse 64X [Ed (B): Neghbourimgblocks availabihty checkingprocesstibd] isinvokedw\ith the current anna location y y (xCurr Curriset equal to (xCb C and thenehbourn lamalocaion( xNbAs y NbAs) amiputs and the outputisassigned tothe blockavaabiityflag aaabeAt. - When aradable~i15 eualto I~tRL' nd MnnModehId[ KNhA; jtvNbtv ] is et tan0 and availableFlaaA is equal to FALSE. the followngapples: - The variable availableFlagA is set equa to TRUE moonnodlldcis set equal to MotionModeld [ NbAs ][ysNbAs], ( y )N isa st qua to (CLbPusX[ xNbAJ][yxN bA ]~ C bPosY[ ~AI [G A ] ) nbW is e eoa to C bWidth[ xNbA I INba J nb~Issaetequa to Chihl x[hA,][y~ ]: mnc pMv isset equal to MoonModelld[xobA][' bAsI+-i and gbudA et equal to C ) bildt txNbA][ JtvNbAs - For Nbeingreplacedbyseither 0orI1the follonmgapphes - WhenPredFlagL X xNbAs Jx'Nb js qual tol3 the deivation proceisfor luma aine conropoitimon eton o ma neighbouringblock as specifidinclause 84A ai' ioked > th teI ua ondg blocklocation ix( b \C b)the lumsacodngblock width andhight (buvdth ebeith he naibourin luma coding block location < Nb ' Nb, n h- hbouring lua ou gblok wdth andhight (nW nhH),and the number ofconra Ipomntmotion 'ectors numCpA vasinput the contolpontmoion vectorpredictor candidates cpM1LXA[ pid] wth cpH -( n rn ipM -I as output Thefollowingassignntsaremade: prdFlagLXA =Pred lagLX[ x~A ][ NbA ] (8-545)

[1651 refldxLXA= RefldxLX[xNbAk}{yNbAk ] (8-546)

SW p- aftine nabiedflag squ to1h ariableaavadablFlaB atequ FALSEand tefollowingapplie fo(x b svNbB ) from (xx~BeNbB,) ( o x~Ba yB: - Th avalah: der'atinnproessfor ablock as peaifiedi mlause 6 4XN[Fa(BB): Ni ehborn hloks available h cekmgproces tbd) imvokd with the current lumal'ocaion xCur y urr) st equa to ( U~b,'C b and henighbourmglumalcation (xNbBse 5 ~B ) a mput andtoutputas asinedo teb lok a'ailabi'flag ailalabiBs - WshenavailableB iqa Ito TRUE ad Montn odelld[ isNbBi yNbBs ]isgreatersta 0 ad availableaBsecul to FALSE tefollowm apple: -The -anable a aableFla is st eqa oTRUE. moonModelldcB is set equalt:o MononModIIdt xNbB y[ T~B ]. ( x. Nb) i s et equal to ( CbPosX[ x~AB ]I y'be ]. CPosY{ xB yNbBI) n bW i set equal to CbWidthxNbBI (yNbB ].nhH is set equal toCbHeghit[ ~B ][ y bhR ] nuCpMv ase equal to MotionModelIdc[xNbBsItvNbBs]-1. and boidxB 'ast qulto Gbilx[ xNbBs,][yNbBI

- ForXben replaedby either 0or1the following applies: -WEhen PedFlagLX( abBs)[IyNbB ] is equal to TRUE the deivation procesfo luma affoecontrolpointmotion ectorsfrom aneighbouringblock asspecifhedimnclause 85i si1noked nith thehima codmgblcklocation [ CbyChbithe lmacodng blokwidth and height acbmidth cbMeight),the neighbourng lumacodineblokloataion x Nb Nb), the neighbouring lunacoding block width and eight ib nbl)b ad the num rof conolponmtionvectorsi nucpM'as inu the control pimtmotion crorpadditor candidats cpMV LXB[c:I ]thepida -0 nutCyM - 1 asoutput

[1661- Thefollowng2assinments aremade: predFlagLXB= Pred lagLX[ xbBII[ NbBk ] (8-547) rfdxLXB =RefldxLX[ xbB ][ yNbflk] (8-548) 5. \\ hensyeaeqeenabledlagiequ tothederationprocessforconstnt econolpoit motionectormerigcandidatesasspcifiedimnclauseSA4.6 isiokedwnhi th ua codingblock location ' a U yCb): the luinacodingblockwuidth and height icbl\idth cbHeih < theaailahibit flagsavaalablea nadlabeA. aaablavaulabeBo aailableBi aableB :.avaableB1as inputs and theaalabiityflags aailabFlagConstK the refeence indicesefetdxLXCostK predictionlist utliationflag pedFkagtXCoratK mton modelndiceotionModelletoantK andcpep L XC onstK[c-pldx] with Xbeng 0 or 1,K = L6 c pidx = 02 as outputs and ait C onstK is set equal to o ni K =1.6.

6. T heniial subblockergingandidate list, nbelMe:ge and ist constructed as follows:

i=0

ubblockMergCandList[+--]=SbCol inha'edlale~gA && 1 :MaduronSubblockMergeCand) subbl[kMergeCad ist[- ]= A i dblelagB &&i -MaxNumnSubblockMergeCand) sublockMereCandt t!i--]= B inavaimbieFlagConstl &&i1<eMaxNumSubbockMergeCand

) ubblockMerg+CandLst[ie- - Const l (8-549) 1 availabieFlagConst2&&i1 <MaxNumSubblockMergeCand) subblockMergeCandiist[s--] -C onst2 iMaxNunSubbockMergeCandi itl availabeFlagConst && subblockMergeCand~isti -- ] - Const3 in availableFiagC-:nst4&&s1MaxNumSublockMerge ad) subblockMergeCandast[s±-- = Consta if avalabieFlagConst5 && i<eMaxNumSubblockMergeCand)i subblockMergeCandEist[i-H}-- Constt itilavalableFlagConst6 && s<aMaxNumSubbioekMergeCand)a sobblockMergeCandat[s -- J ConslE

[1671 7. The riablen urnCurrMrgeCa and inumnOngereCnd aes equaltothenumberofiergm cdidatesnte ubbockMereCad it. 8. When nssmCurMergCand 1ss tha MaxtNumsubblockMergeCani tefollowing is repeated until numnCurrMrgeCand is equal to MaxNsnSubblockMergeCardi wa mero[0] andinvZero[l] both being equal to 0 - The referenceimdices the predictionlitstutlization flags and the motion vectors of zeroCande with m equal to numnCurrMergeCand - nunOnigMergeCand iare derivedas follows refldxL0ZeroCandm 0 (8-550) predFlagLOZeroCandm= 1 (8-551)

cpMvL0ZeroCand,[0]|=mvZero (8-552)

cpMvLOZeroCand[] 1 |=vZero (8-553) cpM-LOZeroandm[ 2]=invZero (8-554) refldxL IZeroCandm= (tilegrouptype == B ) ?0:-1l (8-555) predFlagL1ZeroCand= (tiegrosuptype = = B)?1:0 (8-556)

cpMvL ZeroCandm[ 0]= mvZero (8-557) epMvL1ZeroCandm|[ 1]=mvZero (8-558) cpMvLlZroCandm.[2]|=mvZero (8-559) motionMadelldeZerocandm= 1(8-560)

11681gbildxZeroCandm=0 (8-561)

- ThecanditeroCand withim qualto( u:memrrgcand-numanisf eCand aaaddled at tlieendiofs3ubbocklergeCandit nd numnCui M6egeindi1sincrented byIaEsftollows:

subblockMergetand~t snu urrMergetand-+-]= zeroCansdm (8-562) The variables refldxL8, refidxLl. predFlagLo[ xSbtdx ][fSbldx ]. predFlagLif[xSbldx ]{ySbtdx ] mnvLO[ xSbldx [ ySH dx . mvLl[ xSbtdx ][y Sbids], mnvCL[ xSbldx ][ Sbldx ], and mvCLlf(xSbldx ][ySbldx ]with xSbidx -0.nurnSbX - 1,vSbldx -0-numnSbY - 1 are derived asfobws. If subblockMergeCandLis[ mergsubb kid[fxCb [yC ]IisaequaltoSbCol thei-predction weightimaex bidx is se nqal o8 adthefollowing applheswth Xbemin0 or1:

refldxLX reudxXSbCol (8-563)

- ForxSbdx =.nnrSX- 1,ySbdx =0numSbY - 1,the foowingapplies:

predFlagLX xfbldx ][ySbldxI]= predFlagLXSbCol[ xSbldis][ y~bldxl] (8-564)

FvLX[xSbId] yobbdx[0 ]= mvLXbCol[xSbd ][ySbtdx[0 ] (8-565)

mnvLX[xShldx][fySbdx[1]= mvLXSbCol[xSbldx][ySbldx1] (8-566)

- When predFlagX[xbdx[Sbdx],is equaloi the 1, derivationprocessfor chromamotion vectors in clause 842.13isinoked withimvLX[ xSbIdx ][ySbldx] ad reftdxX input, and te output being mvCLX[ Sbldx ][SbId ]. - The following assignment is made for x=xCb xCb+cbWidth-1I and y =yCb.-yCb +ceHeight - 1:

MonionModeldc x]}{y ]8 (8-567)

- Othermie subbockMegeCandLtegesubockidafxCh ]f Cb jis not equal to SbCol),the following appiw th Xbeing aor 1

[1691

- The fol wn a ianents are made nai N bemn the caddat at positin merge subblock_ix xCbhj[y~b ]imthe subblockm:ergingc caddte astsubbockMergeCandList ( N - ubblockieeeCandist[fmer ge subblockidx fxCb]{ VCbIjI] redx ref-dxt-N (

pre aX[0[1= predagXN (8-569) cpMvLXf8]=cepMvLXN[f8] (8-570) cpMvLX 1 =cepMvLXN[f1] (8-571) cpMvLXf2]= cpMvLXN[f2] (8-572) numCpM = otionModeliN +1 (8-573) gbildx= gstdxl (8-574) - For xSbldx - 0-numSbX - 1,ySbldx --OumnSbY - I the following applies: predFlagLX xSbdx][ySbtdxI]= predFlagLX[801 (8-575) - When predFlagX[ 0If][]is equal to.the deriaionprocess for motion vector array som affmne control poitmotion vectors as specifiedimnsubclaue 84 4 9ismnokedwith the lumnacodngblock location (axCbyothe luma codngblockwidth bWidth theoinsapredicionblock height cbHeight the number ofcontrolpontmton verors numCpgv control poimtmotonvectors cpMLXfepdxlwithcepidx being8 2 and thennube of1 ua com ubblocks in hriontal direction munSBNand in.verticaldrection numaSbY as inputs the lumna ubblockimotion -ecto array mnxL XxSbldx ]{ySbldxl]and the chroia subblock motionvector annvimvCL X{ Sbidx ][fySbldxl withxSbtdx = 0numSbX - 1.,ySbldx =0 .numSbY - 1 as outputs - The following assgnment is made for x=tscb tb-cbWidth-1I and y=yRby h-timht- 1

[1701 MotionModetidex 11v1=numCpuv 1 (8-576>

[171] [Table 4]

&A4.3Derivation proce for subblok-based temporal mergingcandidates

Iputsto this process are: - a locaon xCb,yCb ofthetop-left sample of thcurrent lumacoding blockrelative to the top-left masample ofith currentIpicture, -a variable ebWidth specifying the width of the current coding block in luma saples, - avariableebaeigsecifyingthbehight ofhie cunentcoudngblockm luunasamples. - the avaiabilityflagsavailableFlag~s aaiabielagAi oavalablF ag and MadilbllagBh of the nignbomringlcoding u - thReferin it sTabre dboeeldmLXA. refadxLXf 1, andrefi ofth nei abouringodinguhtdx - thepredictionlist utilization a predFlagLXAo, predFlagLXAs p a XtB:and prkasL XIof merge neighbouring codingunsits, - themotios vectorsin116fractional-sampleaccuracyndda m,inv a 1 AmLHbasand meatoft le neighbouring coding units. Outputs oftisprocess are: - the availabilityvflag avaiableFlagSbCol, d ienhu rofeure (8acdi boihorizontalhdirection mnSbXand inyeicl direction numSbY, - the reference indicesrefidxLaSbCol and refidxLmSbCol, - the mua ntion vectors in 116 fractional-sample accuracy myvLbeSbCol[ xSbdx][ySbdx] and mvLlsbCol[ xSbldx][yslbldx ]withxSbdx=O-nusbX -1, ysbldx =0 numsbY -1, -the prediction list utilization flags predFlagLosbCol[xSb~dx][ySbldx] and predblagLI SbCol[ xhbtdx][ ySbIdx ]withxSbldx= 0.numsSbX - L ySbldx= 0 -numnSbY- 1 - the bi-prediction weight index gbildxSbCoL. The gbildxSbCol is set equal to 0.

[172] Referring to Tables 3and 4above, gbidx may indicate abi-prediction weight index,

gbidxSbColmay indicate abi-prediction weightindex foraa subblock-basedtemporalmerge candidate (eg, atemporal motion vector candidate in asubblock-based merge candidate list),

and in the procedure (8.4.4.3) for deriving the subblock-based temporal merge candidate, the

gbildxSbCol may be derived as 0. That is, the weight index ofthe subblock-based temporal

motion vector candidate may be derived as 0.

[173] Alternatively, weight index information on aweighted average ofsubblock-based

temporal motion vector candidates may be derived based on weight index information on a

temporal center block. For example, the temporal center block may indicate a subblock or sample positioned at the center of the col block or the col block, and specifically, may indicate a subblock positioned at the bottom-right of the four central subblocks or samples of the col block or a sample. For example, in this case, the procedure for deriving the motion vector and reference index in the subblock merge mode, the procedure for deriving the subblock-based temporal merge candidate, and the procedure for deriving the base motion information for the subblock-based temporal merge may be shown in Table 5, Table 6, and Table 7.

[174] [Table 5]

4A.4.2Derivaton process for motion vectors and reference indices in iiubblock merge mAde

Inputso thisprocessare: - a lumnalocation (xCb, yCb )of the top-left sample of the current lumnacoding block relative to the top leftIum sample ofthe current pictu -two variablescebWidth andeblfeightp spcfing the wdt ad teli hegtofth lmnacoding block. Output ofthisprocess are: - t ofluaacodingsbblos inhoizont di on bX din vertical direction nuimSbY,

-~f~ threandidrfdiLad d1 - the prediction list utilization flag arrays predFlagL[ x~bldx][ ySbldx] and predFlagLl[ xhbtdx][ySbldx ], - the luma subblock motion vector arrays in116 fractonsal-amiple accuracy mvL|[ xSbldx][ ySbldx ]and mv1[ xSbldx][ ySbldx ]with xSbldx =n .nubX - 1, ySbldx = 0numibY - 1, - te crm subblock motion vector ay in 1/32 fratonal-sample accuracy mvCLO[ xSbldx ][ ySbId] an vCLl[ x~bldx][ yhbldx ] it xSbdx= O-numbX - 1, ySbldx =OnumaSbY -1, - thpredictionweightindexgbil The vaibe numSbX, nuSbY ad th ubblockmering anidt litsubblekMereCandList are derived bthe followingorderdtpa: 1 Wnp lian panabledflg is equlto1 the followgpplis T he dernvation procesfornreigc caddatas ronsneighoung coding umt appeifiedm clause 54 aimnokedoth deIha codingblock location (xCb. yC )theI ua oadg block widt ebWidth the lua codingbiockheighitcet eight andthe luma codin blockwidt as input adthe output bemg the aalabihti flags axilableFlag~ aailabl.Flag. availableFlagBs aailablFlaBs a avialeFlaB:. th erence mdncesr:efdxLXA0 refldxXAs rfldxLXBs refldxLXB: and refdxLXE thb predctonhit uilizationflags pred lagLXA, pred~layLXAs :-edFlacXBi predlagLXBiand edFlaLX a the motionLvectosnmvLXAtim'LXAsxmLXB m'LXB anLXB .withXbeing0orL

- Thederivation processor ubblock based temporal ergg candidate as specified clause8Ai4 3isinvokedwnith the lumlocatinon xtbyCb) the lumacodngblockwidth cbWidths the lumiacodingbocekheightcb~eght the availability flags availableFlagA:. avaulableFlaeA 1, availabletlagB, availabieFlagfli the reference mdceis refldx(LXA5 refldxLXAi refidxLXBs refidxLXBi the predictionlist utlization flags predflagLXA predFlagLXAi predFlagLXBe predFlaLXtiiand the monionvectorsmnrLXA,mvLXA. msvLXBs mvLXBiasinputs and the output beingthe availability flagavailable~lagsbCol the bi-predictinweightimdex ghidxSbColt:he number of lunacodmngaubblocsinihorontal direction numSbX andinmrtical direction numrSbY the referenceindices refidxL XSbCol the U luma motion vectorsnmvLXSbCol xSbldx ySbldx ]and the predictionlist utilization flags predF lagLXbC ol xSbldxJ[ ySbldx j with xSbldx = 0numSbX-1 ySbldx =0 numiSbY- IandXhem 0or 2. When spsiaffmneenabledflag is equal to 1* the sample locations ( xNbA: yNbA:) ( KNbAi , NbAi) i xNbAr yNbA:), (xKNbBt. 3 Nb~si). :xNb~eiNbB.) ( xNbB: yNbD:) ( xNbtsiNbBs Aand the variables numSbX and numsbYare densednisfollosi ( xAs yAo )= (ixCb - ,yCb+bHeight ) (8-536) ( xA i)I= (ixCbh-1, yCbtc bHeight - 1) (8-537) ( xAi yA2)=( xCb -1, yCb ) (8-538) ( xBs, B )= ( aCb +cbWidth ,yCb - 1) (8-539) (ixBLyB )=( xCb + bWidth -1, yCb - 1) (8-540) {(xB 2 yBj = ( xCb -l1,yCb- 1 ) (8-541)

[1751 (xBisvBt)=(xCb,vCb-1) (8-542)

numSbX= cbWidth »2 (8-543) numuSbY-=cbHeight >2 (8-544) 3. Whentspssaffme enabledftlagtisequal to 1.the vaiable availableFlagA is set equal.to FALSE and the follow mig apphesfor( xNbAs xNbAs.from ixNbAiyNbA: Ito ixNbA i NbAi). -The axadabiht5 deriation proceisfor ablock specified insclauserAX [Ed (BB). Neighbouringblocksaxamdabihty checkigprocesstbd] isinvokedxxoth the current lunmalocaion :(xCurr yCurr )atequal to (Cb Cb and theneighboung ma locaton (N~AS NbA5

) asinputs and the output isasigned tothe blockavailabiitflagaaableAs - When available is equal to TRUE and MotonModelldc{ NNbAi,][ vNbA ]i:s greater than 0 andaxaailabieFlagA is equal to FALSE the followngappies - The variableavaidableFlagA is set equal to TRULEnmononModelldrA is set equal to MotionModelldc[ xNbA1 il][ NbAs ] ( xNb yNb) is set equal to (CbPosX[NbAsI[yNbAI] bPes[xNbAs [yNbAI] n is set equal to CbWidth[ xNbAi ][ yNbAs, nbH is set equal to Cbeight[l'4bAI][ NbAi,] numiCpMv isset equal toMoonModeld[NbA][yNbmAm] - 1and gbiddxAis set equal to Gbmdx xNbAs ]{ NbAsI -For Xbeing replaced by either 0or 1the following applies: - When PredFlagL X[ xNbAs I vNbAs iiequal to 1the deivaionproc esfor luma afnine contrlpout motionvectrsfrom aneighbouringblokas specitiedincilaue854 45is invokedwiuth the luma codingblock location it hxCb oatheuma codngbockwnidth and height -cbWidth. cbHieighi) the neighbouring luma coding block location i ( xNb Nb):the neghbourmngluma codingblock width and height mbW nbH). and the numberof control pointmotionvsectors numL pMv asinput the control ponmtieon vector predictor candidates OpMvLXA[ epldx wimth cpldx = 0 nuinCpMx - 1 as output - Thefollosing assigu.menti are made. pred~lagtXA =Pr ed~lagLX[ xNbA 5 I]{yNbAs1 (8-545) reflxtL XA =RefldsL X[,cNbAk j[yNbAkI] (8-546)

[176]

4. Whenipsaffmeenabledflae equal to 1, the vaableaaableFlaB setequalt FAL SE and the followingapplies foeixNb~s vNbBsfrom (xNbB . yNbB ) tot(xNbB2 ,x'NbB. -The aailablity deniaon process for ablock as specifiedimnclause 6 X[(Ed. fB) Neighsbouring blocks aailabiltcheckigprocess tbd]isinm okedxwith the currentlumsalocation xaCur. Curre1et equalto (xCb yCb ;and theneighbouinginalocation (xNbB yNbBs

) asinputs and the output is asgned to the block aailblityflag aslbeBs - Whenavaiable~ isequal toTRUE and MotinModelldc[ xNhB][xNbBs]isgreeterthan 0 andeavailableFlag isequal to FALSE the folowmn applies -- The variable axeaableFlgilisset equal to TRUEmotionModeldcB isset equalt:o MotionModelldc[ xNbBi][yNbB ]. ( xNb yNb) is set equal to (CbPosX[ xNbABI]{yNbB ]. CbPosY( xNbBsIj[yNbBs ]). nbW is set equal to CbWidth xNbBs][ yNbl ] nbHiset equaloCHeght xNbs ][yNbBI].aumCpyv is set equal toMotonModellde[ xNbll ][ yNbBsI] -1 and gbtidxBisset equalt:o

[17ldx[xh jhel bh ] n - For bemi replacedb either orho -~When PredFlagLN( xhbBs][yNhB ] is equal toTRUR thdenvation processfoelutma affinecontrol pointemotionxectors fromaaneighbourmngblock as specifiedin clause 8.445isinvoked with the lumnacoding block location (xCbyCb. thensumascodng block width and heghtbWidth.cb-eight .theneighbourmg luma codmgblock locaon ( xNb. yNb hthe neghbouring luaacodingblock width and height (nbW nbH), and the number of control pomntmotionx'ectors numnCpMr asinput. the control pontmotion vector predictor candidatescepMvL XB[ c pdx ]withepidx=-0 .. numnCpMv - I asoutput. 11771- The followingassignments are made:

predFlagLXB = PredFlagLX xNbB,{NbBs] (8-547) iefidxLXB =RefldxL X[ xNbBs ][',NbBs ] (8-548

) 5. When spsiaffineenabledflag isequal to 1the deration process forconstrctedffusecontrol point motionvector mergingceandidates atspecified in clause844 6is ii-oked wth the luma codngblock location (ixChvCb the luia cduigblock width andheightcbWidth eHeight> the avalabiit flags avalabekaeadableAs avilableA: avadablellavasdableB 1 ,availableB aalableB: as inputs. and the aaabihy flags aaableFlagConstK. thereferencendices refdsLConstK. preditionlist unzation flagpredFlagLXConatK moionmodelndices mooModelldconstK andcpMvpLXConstK~cpidx] with Xbeng 0 or 1. K=1..6. cpixt 0,2as outputs and bhildxCoentK isetequal to 0withK =1 6

6. The initial subblock merging candidate list, sublockMergeCandList, is constructed as fllows:

i=0 ift avadabkt iagSbeol )

subblockh'ergeCandList[i-+ ] SbCol

[177] sft axadablealagA && iKaMaxNunSubblockMergeCansd) subblockMergeCandLit[ t+]= A ifi avadableFlagB &&i::MaxNun:Subbiockclveraetand )

subbiockMermeCandist[1-H-]= B iti avadableFlagConitl&& i eMxNursSubblockMergeCand )

subblockMergeCandLit[ i-+]= Constl (8-549) ti avadableF lagConst2&&i -:MaxNumsSubblockMergeCand)a subblockMergeCandist[i+-+]= Const2 sft avadabletlagConstl&&iK AexNumiSubblockMergeCand)a sublockiMergeCandait[it- i]= Constl :fi av-lable~lngCont4& iKM:NumSubblorkMergeCasd )

subblockMergeCand2Lit[i-i-i]= Const4 ifi avadableFlagConsts&& i Maxl'umSubblockMergeCansd) subblockMergeCandList[i+±]=--CoastS iff avadableFlagConst6&& t<«MaxNumSubblockMergecand)a subblockMergeC andList[i-+-] C onst6

7. The variable numuCurrMergeCand and numorigMergeCand are set equal to the number of merging 11781candidates in the subblockMergeCandist.

8 I hnnuCurMe gCandislesthan Max~umisubblock erget and. the follewineisrepeated una nmCur geCand a qua to MaxNumSubblockMrgeCnd. th mvZero[0] and mvZero[1] both

sqa - The referenceimdices beml to the preicinl st utilzatiornflags and the motion vectors of zeroCand.with inequal to inumCurrMergeCand- numOnigMergeCand :are dernved as follows re fldxLOZeroem - 0 (8-550) predFlagL0ZeroCandm= 1 (8-551) epMvL0ZeroCand[ 0]= mvZero (8-552) epMvL0ZeroCand[1]=mvZero (8-553) epMvL0ZeroCandm[ 2]= mvZero (8-554) refldxL1ZeroCand=( tileLgrouptpe == B )?0:-1 (8-555) prdlagL1ZeroCandm= (tilegrouaptype == B)?1:0 (8-556) cpMvLlZroCand[ 0 ]= mvZero (8-557) epMvL1ZeroCand{ 1 ]= mvZero (8-558)

cpMvL1ZeroCand[ 2 ]= mvZero (8-559) motionModelldcZeroCandm=1 (8-560)

[1791 gbilaxZeroCandm=0 (8-561)

- Thecanate rCands uwtnmequd to ( C rCig nd- n I ~eC md)i addedat leendofa ubblokuegeCmdt1 nd nu Cn aeuge diinrenenW dbyI low

subbiockMerg eCad 1t[ nCurMergeCand-+]= zeroCand. (8-562)

The variables :eildxU0 retIdxLl1 pred~lagLOLxSbldx11Sbidx ]. predFlagL ilxSbldxIjlySbidx j, isL Oxsbldx ][ 3ShIda nL [ xSbldx1]{y ab~dx1 ], m ] m CLO[xSbidx ]{ ySbldx ]. an mnsCLi[ xSbldx ][ SbIx ] wit NSbldx - nuumSbX - I VSbld - 0 numSbY - 1 are dernved as follows

- If subblockMergeCand ssmergesubblockidx NCb1yCb isaequal to SbCol the prediction weight index obildais set equal to Cand the followimgapphieswith Xbeing0or 1

refixtX efldLX~bol(8-563)

- ForxSbdx= 0-nuSbX- 1,SIdx=0nImSbY- , the followingapplies:

predFlagLX[ xSbldx][ ySbldx ]= predFlagLXSbCol[ xSbldx ][ySbldx ] (8-564)

mvLX[ xSbldx][ ySbdx1] ]=vLXSbCo[x-bldx][ySbldx][0] (8-565)

:vL X-[ xubdx][y %dx][1] mvLXSbCol[xbdx ] Sbdx ][ 1] (8-566)

- When predFlagL X[ xSbdx[ ySbdx is equal to Ithe derivation process orhoma motion 'ectorsindcause85i2 13 isnvoked with mnvL X[xSbldx ][ Sbldx ] nd refidxL Xasinput ad he output bemngimvCL X[xSbldx11[ Sbidx ]

- The following assignment is made for a=xCb-xCb-icb idth- 1 an y =yCb.yCb-i-cebHeight - 1:

MotionModelld[ x ]y]= 0 (8-567)

- Otherise (subblockMergeCandList mergesubblockid[xCb1yCb] is not equal to SbCol), the following applies with Xbeing 0or 1:

[1801

- ~-he follonmg assignments are mod with N being the candidate at positin merge ,ubblock idx{ h][y in ]the subblock merenn candidat hatsubblokaeiet adist (N \s suAblefkMe x=andList mmeg sub kidx, -Cb1][ Cab]] refdxLX=refldxLXN (8-568) pred~lagLiX[ol0] = pred~lagLXN (8-569) cpMvL.XI0 ]=cepMvLXN[01] (8-570) cpMvLX 1]=cepMvLXN[ 1] (8-571) cpMvLX 2 ]= cpMvLXN[ 2] (8-5721) nunpmononMo1d -- 1 (8-5713) gbildx =gbildxN (8-574)

- For xSbldx = 0.numnSbX - 1, Sbldx = O.numSbY - 1, the following applies:

predagLX[ x~bdx][ bldx]= predh layLX[0E][ 0] (8-575)

-When pred~iagL X ][0])is equal to1, the derivation procesfor motion:vector arrays fromaffn controlpoitmotion vectors as specifiedinublae 44isnvoked withthe luna coding bock location ixCb. yCb), the lumsacodingblock width bWidth theuapreditionblock height cbHeight. the number of control pointmotion vectors numCpMv. the control pontmotion vectors epMLX ep1d ] wah ep1d being0 . and the number of lumnscodngsubblocksimnhoizontal c oetonnuSbX anvrcal diretonnuimSbYainput theuma subbok moionvetor aray mvLX[ xShldx ][ySbtdI:]and the chroma sublock motion vector array mvCLX[ xSbIdx ][ Shldx ] with xSbtdx -- 0.numSbX -- 1 yShldx0 --- nSbY -- 1 as outputs. - The following asstrmment is made for x=xChaxCb+cb~idt and y= UCb;Cb -cebHeieht -1:

[181 oouolaldfxi: 1[ 1=num ,~ i 1 (8-576)

[182] [Table 6]

8.43 Derivation process for subbck-based temporalmerging candidates Inputstothisprocess are: -~ a luma location (xCtb, yCb ) of the top-left sample of the current luma coding block relative to the topleft n sample ofth currentpicture, -a variable ebWidth specifying the widthof the current coding block in luma samples - a variablecebHeight specifying the height ofthe current coding block insuma samples. - the availability flags availabeFlagAt, availableFlagAt, availableFlagBs and avaibleFagBh of the neighboring coding units, - the reference indices refdxLXAerrefldxLXA 1 ,refldxLXfl, and refdxLXBi ofthe neighbouring coding units, - the prediction list utilization flags predFlagLXAs, pred~lagLXAi predFlagLiXtl, and predFlagliof the neighbouring coding units, -the motion vectors in 1/16factional-sample accuracy mvLXAs, mvLXAs mvLXBs, andnmvLX~a of the neighbouring coding units. Outputs of this process are: - theavailabiltyflagavailableFlagShnol, - thenmber of luma coding subblocks in horizontal directionmunSbX and invertical direction numSbY, - the reference indicesarefldxLOdbColandrehdxLbCol,

- the lsuma motion vectors in 1/16 fractional-sample accuracy mvLOSbCol[xSbldx][ySbldx] and mvLISbCol[xSbldx ][ ySbldx ]with xSbdx= 0..numSbX - 1,.ySbidx =0 - numsSbY - 1, - the prediction list utilization flags predFlagLOSbCol[xShldx}[ySbldx] and predFlagLlSbCol[ xSbdx ][ySbdx ]with xSbIdx = D.numSbX-I1, ysbdx =0 -numnSbY- 1, - the bi-prediction weightsindex gbildxSbfoL The availability flag availableFlagSbCol is derived as folows.

- If one or mor of te folowing onditions is true, availableFlagSbColisaset equal to 0. -tile_group~temporalinvpenableflag is equal to 0. - apsbttmvpfag is equal to O - cb~dshslessthan8. - ebHieight isletsthan&8 - Otherwise, the following ordered steps apply: 1 Fhelocation !x<th yath of the topleftample ofshuaodngtreelockthat cotimthe current codingblock and the location (xflt yCtr )of the belowright centereasple of thec urent luacodingblock arederied asfollows

xCth = (xCb >>CtLo2Size )« CtuLog2Size (-577)

yCth =(yCb >> Cuog2Size)« CtLog2Size (8-578)

xCfr =xCb - (ceb uidth 2) (8-579)

yCtr =yCb +(cebHeight /2 ) (8-580)

The luma location (xColCtrCb, yColCtrCb )is set eqa to hestop-ef sample of the collocatedlouma 2. codmg block covering the location given by(KCtr yCt) isde ColWi relative to the top-left lumsa 1131amole ofthe collocated picture specified by CoPic.

SThederation poces for ubblok-baed temporal mergg base motion data as specified m ca 4 s44smvkedi 4u th thelocaion( xCth Cththelocaton C"oIC b ColrCh) the avaiabihit flags avalableFlagA aadlableFlagAp aailableFlaB,:end aaableFagB: and the prediction his utilization flags predFlagLXAi. predFlagLXAp predflagLXB, and predFlagLXB .and the referenceindicesirefldxLXAn refldxLXA reldxLXflsand refldxLXB and the moton vectors mLXAs-mvLXA 1 -mvLXBandntXBwithXbemn0and1,as puts and thenmotionxectorsctrMvi.X the predictionlist utiliraton flaoitrPredslaTLX and the reference indices ctrRefldxL Xof the collocated block with Xbeing 0and 1. the bi-predicron weightindex gbiddxSbCol, and the tempor almoion vector tempMV asoutpts 4. Thexarnable availablef lagSbColis dern ed as folos. - If both cirPredFlagt0oandcetrPredFlagL are equal to 0.availableFlagsbCol istet equal toO0 - Oherwse availableFlaSbCol is set equal to When availableFlagsbCol is equalto 1the followingapplies: - The variables numSbX, numSbY, bWidth, sbHeight and refidstLXSbC olarne drved a sfolows

numSbX =ch\dth»3 (8-581)

numSbY = cbtteight»>3 (8-582)

sbWidth = cbWidth /numSbX (8-583)

abtteight =cHfeight numnSY (8-584)

refldxLXSbCol = 0 (8-585)

- For xSbldx- 0numSbX- 1 and ysbidx- 0niumSbY- , the motion vector mvLXSbCol[ xSbldx ][ ySbdx]) and prediction Eist utilzation flags

[1841predilagLXSbCol[xShldx][ySbldx}arederivedasfolows

- Thetusloca-ion,' Sh peiy the op leaml e. fhecurrentcodmgsubb kelae thetop-left luma sample of th amnt picti derived afollw: aSbh xCb +xSbldx 'bWsdt (8-586)

ySb yCb +ySbdx*sbeight (8-587)

- The location (xColSb, yColSb )of theolcaesbblock inside ColPics derived asfolows. xColsb =Clip3(xNEtb, Mm (.urmic idthlrkampleY - 1,xCtb+ (1 « CtLog2SizeY)+-3),(8-588) xSb--(temp 0]i4))

yColSb= Clip3( yCtb, Mlin( CurPicteightnSamnplesY- 1, yCtb+ ( 1 « CtbLog2SizeY)- 1), (8-589) ySb + (tempMV[] »4)

) - The vamblecurrChspecfiesthe hinacoding blockcovering the current codingsubblockinsidethe currentpicture.

-The variable colCb specifies the luma codhng block covering the modified location genby ( (xColSb»3)3yColS»^ 3 )<3inde the CoiPc - The lunsalocation ( CoICh yv olisaset equal to the tpdelisample of theclocated luma cdin block specinled by colebrelativeto the toplethluma sample of theollocated picture specified by ColPic - Thedenivationprocessfor collocated motion vectors as specifiedimnclause SA.212anvoked with currCb colCb.( xColCb vColC )reixL seequal tooatnd shFtaset equal to 3as inputs and the outputbteingassined to themoion vector ofthe subbok nLOSbCol[ xSbldx ][ySbidx ]and availableFlaeLoSbcol

Thedarivation procasfor collocated motion vectorsas specifiedimnclause8Sul.2ianvoked with currCb colCb , xClCb vColCb), refidLl set equal to 0atndshFlagsetequal to 1asinputs:md the output beingassined to themoion vector ofthe sublockmuLtSbCol[ x~bdx][ysbldx jand availablegagt1Mbcl,

-WhenavailablegLagOSbeol andavailableFlagLSbColraboth equalto0, thefeolloigappliesforXN being 0ad 1:

mvLXSbCol[ xftbdx ][ySbIdx ]=ctrMvLX (8-590)

pred~lagLXSbCol[ x hdx][ySbldx ] trPredFlagLX (8-591)

[1851

[186] [Table 7]

S44.4Derivation process forsubblock based temporal merging base motion data

Inutcoths pocess are: - telocanon (xCtb,yCtb )ofthe top-ef sapieofthelumnacoding tree blockcthat contan tecrentccdg block, - the location ( xolCtrCb, y~olCtrCb) ofthectop-left sample of the colocated luma codngblock that coers the below-right centersample. - the availability flags availablFla~ aailabie gsaailable ag~ ad avaiabe1a~ of the neighbouring cdg uits, - he reerenc is rfdxLX lefdxLXA. effdxLXB. adcl refxXflofthnighbotrngcodn uitt, - he prdionst utiliation flags predIagX , predlagLXAis 1rdagXBeand prdlgLXBi ofth neighbung cdg unts - the ion vcrs in116fratin-ampleaccacyi mLXA5 m LXA invLXe invLXB of the neighbouring cod unts.

Outputs of this process are: - the motion ectors crMvLO and crMvL1. - the prediction list utilization flagsctrPredFlagLOeand ctrPredFlagL1,

- te referene india eRefx adctrRef 1

- the temporal motion vector temnpMV,

- thehbi-prediction weight index gbildxSbCol

The variable pMvissetasfollows:

sem pm [0]: 0 (8-592)

tepMv[ 1]=0 (8-593)

The varibe crPic specifies the current picture.

The vaia aviablellagN is set equal to FALSE, and the folowmg applies: - When atail ag~ is equal to 1.the following applies: - a-aiablFlaNi e equa toTRUE. - refkIlxLXNis set equal to refldxLXA andasvLXN isset equal toinvLXA 5 ,forXbetmgreplaced by 0and

- When availabieFlagN is equal to FALSB and availableFlagLB1iequato1 th eollowna phies - avaiiableFlagN issetequalitoTRUE

- refldxLXN is set equal to refidxL i n vXN isset equa 1ton vLXBi foX eingeplaced by ofor - When availableFlagN is equal to FAL SE and availableFlag~ is equalt 1,tefollowing applies: - availableFlagN is set equal to TRUE. - r XN et ualto ft XBiand mvLXN i t q toivXbforX ui placed by

- When available~lagN is equal to FAL SE and availableFlagAcis equal to1, the following applies: - available~laN is set equal to TRUE. - refldxLXN is setequal to refidLXA 1 adinnLXN ssetequaltomvor Bfr bngyrpaed by o andI1 D dL When availableFlagN isaeualto TRUE, the folowing applies: 01 and 1. - If all of the following conditions ae tu, tempMV isset equal tomvLIN:

predFlaL N is equ to1, - D iffi~dernt(Col~ic, RefPicList1[refldxLIN]) is equal to 0, - Difti~derCnt(aPieurie)is less thnorequal to 0for every picture Pic invery r efence picture list of the current tile group, - tilegrouptype isequaltoB, - collocaed from_10flag is equal to0. - Othenvise if all of the followingconditions are true, temspMV is set equal to mvLON:

- 1aON i ualto1, - D i~cderCt(olPic, ReficListO[refldxLON]) is equal to 0

[1871 The location (xColCb, yColCb )of the collocated block inside ColPic is derived as follows.

xsColCb =Clip3( xCtb, Min(CurPicWidthlnSamplesY - 1, xCt+(1 CtbLog2SizeY)+ 3)(-59 4) xColCtrCb+ (tenmpMv[] » 4) )

yColCb= Chipy Ctbt Mm: CurP icHeightlnSamnplesY - 1, yCtb+ (1 CtbtogSe Y)i- 1}) (8-5 95) ycl tcb +( tempMv[] » 4) )

ThearraycolPredModessetequaltothepredictonmodearrayCuPredModeofthe collocated picture specifiedby ColPic The motion vectors crMvLO and etMvL1, tepredction Ist utirzaton flagsctrPredFagLO and ctrPredFlagL1, and the reference indices ctrRefldxLO and cirRefldxL 1are derived as follows: - If colPredMode[xCoIC][yColCb] is equal to MODE INTER, the following applies: - The variable cuChspecifies the luinacoding block covermug ( xtCb ,yCtrCb )inside the current picture. - Thevariable coiCbhspecifies the loma codng block coverminghemodified locationgivn-eb ((ixCoIW3A)<, ( yCoCh»3) is imde the Coicr - Thessuma location xCoIli.yColCb isset equal to the topleft sample ofhe collocatedloins codingblock specified by col~b relative to the topleftina saple of the collocatedppcue specified byColPic. 618811

- -- hedermvtion pmoenfortempomalmotionvector prediction inubue A412iainvoked with currCb colCh. ixColC. yColCb)centerRefdxLO and bFlagtoequal to Iatioputs andt'he output bemi ngned tocetrMvi.C and:tr~rdFlagI.O - Th denvationproce fortmporal motionxec predctionim ubelause 8'22imnvked i currCh coiCb. (CoCb ColCb)cenerReldxL ad bFlaget equal to 1at inputs and the output bemngaaaigned tocetrMvL iand etrPredi lagL 1.

ctrPred~lagLO =0 (8-596)

ctrPred~lagL =0 (8-597)

[1891

[1901 Referring to Table 5, Table 6, and Table 7, gbidx may indicate abi-prediction weight index, and gbildxSbCol may indicate abi-prediction weight index for asubblock-based

temporal merge candidate (eg, atemporal motion vector candidate in asubblock-based merge

candidate list).<} In the procedure (8.4.4.4) for deriving base motion information on

subblock-based temporal merge, the gbildxSbCol may be derived as gbidxcolCb. That is,

the weight index of the subblock-based temporal motion vector candidate may be derived as

the weight index of the temporal center block. For example, the temporal center block may

indicate asubblock or sample positioned at the center of the col block or the col block, and

specifically, may indicate asubblock positioned at the bottom-right of the four central

subblocks or samples of the col block or asample.

[1911 Alternatively, the weight index information on the weighted average of the subblock

based temporal motion vector candidates may bederived based on the weight index

information in units of each subblock, and may be derived erived based on the weight index

information on the temporal center block when the subblock is not available. For example,

the temporal center block may indicate asubblock or sample positioned at the center of the col

block or the col block, and specifically, may indicate asubblock positioned at the bottom-right

of the four central subblocks or samples of the col block ora sample. For example, in this

case, the procedure for deriving the motion vector and reference index in the subblock merge mode, the procedure for deriving the subblock-based temporal merge candidate, and the procedure for deriving the base motion information for the subblock-based temporal merge may be shown in Table 8, Table 9, and Table 10.

[192] [Table 8]

AA.2Deriation process for motion ecors and reference indices insubblock merge mode

Inputsto thisprocessare: -a lumialocation (xCb, yCb )of the top-lIeftsample of the currenluma coding block relative to theiop left a a of t entpiture - two abl ebid and Heghtpecingth widthnd heigtofthel a ngblok

Out fth process are - theumberof ua cigubbkshorizontal dirtion numSbXand in vertical diretinumSbY

- the referenceimdices efldxLO and refldxL1, - the prediction list utilization flag arrays predFlagL[xSbldx][ySbldx] and predFlgL1[ xSbldxI][ySbldx ], - the lutnasubblock motion vetor arraysin1/16 fractionaL-sample accuracy mvLO[ xSbldx ][ySbldxI] ad mvL1[ xSbIdx}[ ySbldx ]withxsbldx =.n -uSbX - 1, ySbIdx= 0-numSbY -1 - techrm subblock motonvector arasi 32 factional-sample accuracy mvCLD[xSbtdd][ ySbldx ] ad mvCL1[ xSbldx }[ySbldx ]with xSbIdx 0-nuSbX - I, ySbldx= O~num~bY - 1, - tebi-prediction weight index~ -blx

The variables numSbX, numSbY and the subbock mergngcandidate ist subbockMegeCandList are derived by the following ordered steps: 1 When spssbtnypenabledflag is equal to 1the foovng applies - The demi ation processfor mergmig candidates ham neighbouiing coding umts as pecified :n clause 34. 3 is iokdxithe lua cadimgbink loaon ( Ch C b) Ihlua ,odm blo:Lk idth :bui dhtheI ua codingblock hight ebHight ad tn lua codmgblok u dlh asi mpts nd he outu bimg he avaabit flag, ~alableFlaA asailableFlagA avadablIFlagB. a baiFlaB andaalblFlagB th werece ndice,ef~dL A nt~dL XA1 refidxXBretL XB and refdL XE, he p&iition 11fthztion flag, plgIA pI XA* pdF gLXBpedFagLXiand pteIagLXB d he motion aclors nnLN un LXAmiLXB nmIXB andim XB ;abhXhbemp a01 1

- The derivation process for ubblock-based temporal mergingcandidamesas specifiedin clause8443 isinvokedwth theuimalocanson ?xCb VCbh)the lumacodogblock width cbWidtli the lumnacodmngblock height cbHeight the avalability flags availableFacA: avaclableFlagAi aralableFlagllo avadlableFlagi the reference indices refldxLXAc refldxLXA: refldxL X~s reftdxILXBi the predictionlit utibizationflags predelaXA pwedflgLXAi pwed~lagLXE predFbeLXBi andthemnouionsectorsm:nLXA; mxLXA:~ mnvLX~i mvtNX asusputs and the output bengthe avalabiity flag avalableFlagSbCol the number of luinacodingsubblocks inhoizontal direction numSXa:mdimnvertical direction snmShY. the reference indices refldxLXSbCol, the bi prediction weight index gbildxsbcoll xSbidx]J[ySbdxIj.theuimasmotion vectors mviXSbCol[ xSbldxIJE Sbldx and the prediction list utilzation flags predFlagLXShbcol~xShldx}[vSbldxJ with xSbldx= 0.numSbX - I, ySbldx=0 .nurnSbY - 1 and Xbeing 0or L 2. When syaffmneenabledflag is eual to I* the sample locations xNb-\ yNo\[I. (bA iyNbAi ( x NbAtyob i (i E vNbBs ( xNBiNbBi) (cxiNbB: yNbBm) (NhBi- NbB),a'md the-aiambletnumShXarnd numShY arederied asfollows (xAe~yAe)=(xCb-1,yCb cbHeight) (8-536) ( xAi yAt)=t(xCb-l1yCb+cbHeight -t1) (8-537) ( xAi yA )=I(xCb - 1, yCb ) (8-538) (xxBi yf, :=•xCbI- chWidthyu-1 1)i (8-539) ( xBi5 Bi :=( -b~cWidth -l.- -1) (8-540) ( xBs yB2)= ( xCb - 1,yCb - 1) (8-541)

[1931 (xBi yB)=(xChytsh-1 ) (8-542)

numnSbX- cbWidth>» 2 (83543) nusbY chibJeight >>2 (8-544) 3. When spaaffmneenabled flags equal to1,.thevaiable ailabieFlagAis set equal to FALSE and the followingapplis for( xNhAsVNbAs yfromnt xNlmAsyNbAiyto ixNhAivNbAi - The availabiityderivation procesfor ablock as specified in clause 4X [Ed(BBh Neighbouing blocks avadailty checking proestbd] isinvokedsvih thecurrent lmnslocation ! ( xCury Curri-)set equal to (xcC b~ and the neigbhouring luma location NbA sNbA 5

) asinputs and the outputsassigned tothe blockavailabityflag available 5

- When availableA iiequalstoTRUEand MonionModellde[ xNbAs ][ yNo.As greater than 0 and avadlableflagA iiequal to FAL SE the folouingappies The variable avaslble~agAisset equal toTRE motionModeldAisset equal to MeotnonMcdelidc[ xNbA 5 ][ yNbAs) ( xNbhyNb ) is set equal to ( CbPosX[ xNbA ]J yNba] C bPoY[ xNbA j{ yNbA }I). nbW is set equal to CbWidth[ xNbAi)y~bi ]. nbHisset equal to CeighlxNoj[ yNbAcI, numCpMv isset equal to onModldc[xNb 5 ][vNbt ]-- I and gb;idxA is set equal to Gbildx[xNNbA ] yNbAs ]

- For Xbeingreplaced by either Oor 1.the following appie - When PredFlagLX[ xNbA][ 5NbA 5 isequal to 1the deanion pocesfo:humaaffine control point motion ectors from aneighbourngblock asspecifiedimnclauseSAA44 is ivokedwth the luimacodingblock location xC b b 1y ithe _unacodngblockwidth and height (chid1th, cbHeght) the neighboring luins coding block location (xbyNb,the neighbourngluma codngblcks-dthiand height (nb\\ nbH),and the number ofconol pointmotionsectorsnumt pMvasinput thecoenrolpontmoton vetopehictonidates cpuvLX\[rphd] withcepd -0 numCpu -1 as outputL - The followvingassignments are made: predFlagLXA=PreJFlagLX[.dbA jlxNbA5 ] (8-545) refldxLXA =RefldZLX[ tNbAk ][yNNbAk]1 (3-546)

[194]

4. When spsafineenabledflagit equalto 1.theanabletsubbehFlgBisseteulto FALS3-amd the following applies fort;xl'TBsyNb~ ) from NNbfs yNbHo )to ixNbH yxbBB) - The availabilty deriaton process for ablock as specifiedin clause 64X[Ed. (BB): Neighsbournoblocks axalabiity checkingprocess tbd] isinvokedwiththiecurrenttlumaslocanion ( xCurr. yCurr )aet equal to ixCb yCb )and theneighbounn luma location (xNbB yNbBc) asinputs and the outputitassigned to the block avadlability flagavaidableB& - When aablesiiequal to TRUE and MouonModelld[ xNbB][3NbBtisgreate than 0 and axalableFlagB isequalto FALSE the followineapplie - he variable avadablelagB is setequal toTIRUEKnmotionModeldc itset equal to MotionMorielldc[ xNb~a ][yNbBs ] ( xNb yN) isr: set equal to (CbPosX[ xNbAB]y NbBs, CbPosY[ xNbBs ][yNbBcD] nbW is set equal to Cbx~dth[xxbBsI][ NbBsjnbHis set equal to Cbeight[ xNbBs][y ObBs ]numnCpMv isset equal to MtoModelld[ xNbBc ][ VNhBs]+ 1 andgbdsBiaset equal to Gbildx( xN bB5 }{VNbc l

. - ForXbeinreop lacedbtheror 1,the following applies: - When PredFlagT X[mxNbB 5 [ NBe]ieual toTR UFthe derivation procesforlhima affmnecontrol poumtmotion vectors fiama neighbouring block atspecifiedimnclause S 4.4 isinvokedwith theRusna codingblock location ixCb.yCb ).the lumnacodng blocktridth and heght ichWsdthcbfleight the nihbourmnglumacodnmgblock location ( xNb. VNb 1the neighbouring lumnacodingblock width and height mbWunbHi)and the number of control pointmotion vectors nuinCpMv asinput. the control pomtmotion vector predictor candidate cpMvL XB[cpldx ]withcepldx=0 nunsfpMv - 1astoutput. " eflo "'""me"2" 11951 "

predhlagfB-=Pred~lgLX[x~bBsI][yNb~s] (8-547) retldxLXB -RefldxLX{ xNbBi j{ yNbBs ] 80548

) 5. W henspa_affine_enabled~flag is equal toI1.the derivation procesfor constructed affinecontrol point motioniettor mergcandiidatesasspecifiedimnclause 84 4 6is isokedxxsth the loinsioduagblock location i Cb. yCb),theltoinscoding block width and height cbWidth. clleight,the avalability flags ailableAs axadlableA 1 .axadlableAs aiahieblesaxailablefBi axadablef 2 aaialableB a input and theaalablity flags aailbleFlagConstK. the referencendies refdxLXConstK predictionlist utiizationflags predlagLXConstK motion modeldicesotonModeldcConstK and cpMvpLXConstKiepldxj with X being 0 or , K=1 6,cpidx=0.2 at outputs and gbildxConstK is set equal to with K- 1 .6. 6. The inital subblock mmegcandidatelihtsbbiockMeendListisconwtruceas follow i=ti iffavatlableFlagSbaol subblockMergeCandListt c+) - SbCol ift a'ailableFlagA &&i c: MaxNumnSubblockMergeCand)i tubblockMergeCandLit~I l=A if( avaclableF lagB && i<MaxNmSubblockMergeCand)i subblockMergeCanditt c++]= B ift axailableF lagConstl && i<eMaxNunSubblockMergeCand) tubblockMergeCandLiatt 1-++ -Constl (8-549) ifl avaclableFlagConst2 &&i1 MaxNuniSubblockMergeC and) subblockMergecandList[c++ = Const2 lagConst3&&i1 MaxNunsubblockMergeCand) iff availables tubblockMergeCandiisti e+]- Const3 ift availableFlagConsta && iccMaxNumnSubbockMergeCand) subblockMergeCandL stts-+] = Const4 ift axailableF lagConsttt&&icceMaxNunSubblockMergeCand) subblockMergeCandLit!+I- = ConstS ifl availableFlagConst6 &&ic-cMaxNunSubblockMergeCand) susbblockMergeCandList[c++] Const6

[1961

7 Thei alnincnurMereand andnmunigergCandareseatequal to the:umnbeofeingm

8. Whe:nnumnCurMergeC andis lessthan MaxuubtobckMerge and :he folloxvsneisrepeated until nomCurrMrgeCadiasequal to Madum~ubblockMereeCand wh mxZewi[01andumwZero[1l both beng equal to - The reference indices, the predsiction list utilization flags and themoion ze:-Candaiwith vectioriof in equal to (numnCurrMergeCand -numnOrigMergeCand derive das folows 3are refudxLDZeroCand.= 0 (8-550) predFlagLoZeroCandm= 1 (8-551) cpMvLOZeroCand[0 ]= mvZero (8-552) cpMvL0ZeroCand[ 1]= mvZero (8-553) cpMvL0Zerollanda[ 2]= nvZero (8-554) redxL1ZeroCand=( tilegrouptype == B)?O: -l (8555)

predFlagLlZeroCandm= (tileerouptype - B ) ?1 :0 (8-556) cpMvL1ZeroCand,,[0]-mvZero (8-557) cpMvL1ZeroCand[ 1 ]=nmvZero (8-558) cpMvLlZeroCand[ 2 ]= mvZero (8-559) motionModelldeZeroCandm = 1 (8-560)

[197] 11971gbildxZeroCandm= 0 (8-561)

- The canddate meCand withm equal to inumCurrMergsCand -numerigMergeCand )is addiedat the end ofsubblockMergeCand isandInumCurrMergeCandisncrementedby1afolows: subblockMergeCandList{numCurrMergeCand--+]= zeroCanda (8 562) The variables refldxLQ. refidxLl predFlagt0[ xSbldx ][yVSbdx ] predFlagL1[ xSbldx]{[ySbld ]. mv'i shlbdx ][ySbldx I mv 1[ xnbdx][ ySbidxj. mvCLO xbidx ][y5bIdxl1 and mx'CL1[ixSbldx ][yvbIdx ]with xSbldx = 0.numSbNX- 1\SbIdx =0nun~Y - 1are derived asfolows - If subblockdergeCandLit[ mergesubblockdxxCb ][yCb ]isequal to SbCol thehi-predction weightindexegbildsaset equal to Oand the folowngapplieswith Xbeng Oor1i refdxLX=redxLXSbCol (8-563)

-FrxSbldx =0numiSbX- 1 ytSb)di = 0mmSbY - , thefolowing applies:

predFlagLX[ xSbldx ][ySbldxI] predFlagLXSbCol[ xSbldx ]{ySbldx1] (8-564)

mxLXi xaldx ]{ ybldx][0]=snmvLXholl xbbldx ][ybdx ][0e] (8-565)

mvLX[ xSbtdx1][ySbldx11]= mvLXSbCol[ xbbdx ][ySbldx ][ 1] (8-566)

- XWhen p,ri, agLX x~idxA< j[ T y~la j . ua te l5the i.rwaion process .r hroa mt,

vectors o lause84213isnmvoked with mvLX[ xSbldx ][vbldx ]and refldxLX asnputs. and the output beingmvCLX{ x~bdidy]{vbdx3 - The tollownmg asgnment is made for x=xCb__xCb+cbidt- 1 and = bCbc - ehght- t

Moino dhdc x ][ y ]=0 (8-567)

-Otherwie !subblock~rgeandit[meesboki[ xCb ] 0b ]iinoequalto SbCol), the folloiine apieswth Nbeming or1

[1981

- The folowsmg aassaenes are tmads with N bemoe the candidate at position merge subblock idx[rcb][ VCb]imnthetbblockemingucandidateist subblockhergecandLt SN =aubbiockMergecandLitmerge mbblockidxxCb ][ yCb ] ]) refldxLX=refldxLXN (8-568)

predFlagLX[ 0][ 0]= predFlagLXN (8-569) epMvLX[ 0]=cepMvLXN[ 0] (8-570) cpMvLX 1]=epMvLXN[ 1} (8-571) cpMvLX[2]=epMvLXN[2] (8-572) umnCpMv motionModeldxN + 1 (8-573) gbildx = gbildxN (8-574) - For xSbTdx =0-umhbX -, Sbtdx =-urnSbY -,the followingapplies:

predFlagLX[ xSbldx][ ySbldx ]=predFlagLX[ 0][ 0] (8-575) - When predFagLXO[0 ]0is equal to1. thederivaionprocessfor moionvectorarrays from affine contrlpoimoionectoirs asspcifiedumsutbclaue8a 4 9sinmokedwith thetluma codngblock location : Cb yCb) the mecodngblock widthcbeidh.the lumapredctionblock height c Height. then:mmber of control point motion vectors numCpMv the contropontmotion vectrsep31vL N(cpdx| uwithcptdxbeing0..and the number oflhsacdngabblockeinhorzontaldJuretnionnmbX andin vertial direction numSbY asinputs the luma subbockcmotionvector anayomvL X[ Sbldx ][ySbdx ] and th chroma subblock moIon vector array:nvCLX bId][ ySbldx]withxSbdx=0nums bX ySbldx---0 inSbY-- Ias oiuts. - The following assignment is made for x = Cb -xCb +cbWidth - 1 and y= yCb-yCb +cbHeigh -1:

11991 MotionModeldl x][vy]=numCpMV - 1 (8-576)

[200] [Table 9]

&4.43Derivation process forsubblock-basedttemporaltmerging candidates Inputs to this process are: - a hunaslocation (sxCb~yCb )of the top-left sample of the current luma coding block relative to the top-left huna sample of the current picture, -a variablecebWidth specifying the width ofthe current coding block inluma samples, -a variableceHieight specifying the height ofthe current coding block in luma samples. - the availability flags availableFlagAs, availableFlagAi. availableFlagfls. andavilableFlagB of the neighibousringc ogunits - thereferencelndes refldxLXA, refdxLXA1, rffdxiLXNEsand refldxLXlt ofthe neighbouring coding units. - the prediction list utilizatiosflags predFlagLXAs, predFlagI ,pred lgLX, and predFlagLXBltof the neighbouring coding units, - theamotion vectors in 116fractionl-sampeaccuracynvLXA, mvLXA,mvLX * and mvLXB1of the neighbouring coding uts.

- the nsniberofhuna coding subblocks insorizontal directionumsSbX and inverical direction numSbY, -the reference indices refldxL0SbColeand reffdxLlISbCol,

- the huna motion vectors in 1/16 fractional-sample accuracy mvLOSbCol[ x~bdx][ ySbdx ]and mvL5SbCol[ xSbdx ][ ySbdx ]with xSbidx= 0-nusmSbX - 1,ySbldx =0 numSbY - 1, - she bi-prediction weight index gbildxSbCol[xkbldx][yibldx], the prediction list utilization flags predIagOSbCol[ xSbldx ][ ySbldx ] and predFlagLlSbCol[ xSbld ][ySbId ] with xSbkdx 0.numSbX -I, ySbldx = 0. sumSbY - L.

The availability flag availableFlagsbColiis derived as follows. - If one or more of the followngconditions is trueavailableFlagSbCol is set equal to 0. -~ tieegroup inmpratomv enable flag is equal to 0 - spssht a iseeq tot0 -cbWdth is sthn8

- bHeight ie e - Otherwise, the following ordered steps apply: L The location (xCtb yCb ) of the top-leftsample of theuacoingptree blockhat conamnsthe current coding block and the location (xCnr, yCtr )of the belw-rghce ntersample of -heurrena lumacoding block are derived as follows: xCtb =( xCb>>CiLog2Size ) «CuLo2Size (8-577)

yCtb=(KyCh>>CuLog2Size ) «CtuLog2Size (8-578)

xCtr = xCb4(ch Width/2) (8-579)

yCtr yCb+(cHeight 2) (8-580)

2. Thelunma locatn C olCtrCb C olCrCbisetqalto thetpeftample ofthecolocatedhima codingblockcoveing the location given by Cs-yCtr3inside ColPicrelatin-eto the top-left luna

[2011 3. ThedJ--:nation pocsfor sublock-based temnpar migrba emotiondataspecifiedin clause54 4 4A:rnvokedw-uth thelocation /xCthbyC th I the location :xCoalCtrChyiColCtrb): the availahsihtsvflasadlableflapAs avaulableFlap~a aableFlagfDand a-aiableFlagB, and the prediction list utilization flag predrlagLXA, piedFlagXA, pr dlayLX ad predFlagLXB 5 .and the referenceindices refldxLXAtrefidxXA reftdXB, andefidxLXD1 ad the moine ctorm'LXA mvL XA1 m L XBs anxL XB h X beingaand. asimput ndtheminaonvectos 'cr LX the predicionlit ulihzinfage rdFl8X an erefrenc indices etrRefidkL of the collocated block with Xbeming and 1,theh-prectineightinex ctrbildx andt:he tempor almoionviec toresmpMlyas output 4. ThevarialeaalableFlagbColis demivedasfoMlos - IfbothctrPredFlagL OandcetrPredFlagLiare equal to0, availableFlagbbCo is set equal to 0. -Otherwise availableFlagSbCol is set equal to L When avaiableFlagsbColis equal toI thefollowingappies - The variablesnuSbXnnuShY sbWidth, sbHeight adtl re~xXSb ol aedernved as follows:

numSbX = cbWidth>» 3 (8-581)

numSbY = cbHleight »3 (8-582)

sbWidt = bWidt n nuSbX (8-583)

sb~feight =cebfeight /numuSbY (8-584)

reffdxLXSbCol = 0 (8-585)

- For xSbldx=0-nuimSbX- 1 and yMidx-0 nusbY- I, the motion vectors nsvLXSbcu![ xSldx ][Sbldx]j nd predictin hist utilization flags pred E XSbaoI xSbldx ]Iyh aIe deemed follows:

[202]

- The lualocaton x bybpein mhe tplef mpieof e tnodmngsubblockrelative tothetop-leftlumasampleof ee pentrt folfls as .deed

xSb = xCb + xSbldx * b h (8-586)

ySb =yCb +ySbldx *tbHeIt (8-587)

- The location (xColSb, yColSb )of the collocated subblock inside CoPic isderivedasfollows.

xColSb= Clip3( xCth, Min( CurPicWidthnSamplesY - 1,xCtb+( CtbLog2SizeY )+ 3 )(8-58 8) xSb+(tepV[ ] » 4))

yCoISb= C hp3(-.tb, Min(CurPicEcightinSamplesY -1 Chb- -I « CtbLog2SizeY)-)3, (8-5 89) SSb- (tempu[]»4))

- ThevariableurCbspecifiesthenlma coding blockov gthe cent codig subbckinside the current picture. - ThevariablecolCspecifiesthe luma coding blockcoveringthe modifiedlocationgivenby ( (xColSb>3 ) « 3,(yColSb »3>)«3 )insideh ColPie - Thehlsna location (xColCb, yColCb)istset equa tothe tp-ef sapie ofthe collocated luma coding block specified by coiCbrelative to the top-left luma sample of the collocated picture specified by ColPic.

[2031 ThegbirdxsbCol[xsbldx][ysbldx~issetequaltogidxcelCb - The derivation process for collocated motion vectors specified incelauseSA2 12 isinvokedith curnCb oICb. (xaok byGolb)ef:-edxLset equal to aand iblaget equal to 1ainputsand the output being assgned to the motion vector of the subblock mvLOSbCoL[ xSbldx ][ysbldx ] and availableFlagh0SbCol

- The denvation processfor collocaedoonvectors atspecified in clause 8A4 'is invoked wth curreb.:oktIhK~xob CoI b :efldx1 seteqal to 0an sbFacst equal to1ainputsand the output being asignedstohe motornector of the subblock mvLSbCoi[xSbldx][ySbidx ] and availableFlagLISbCol. - Whenaa~iaaht ~aSbaoand availbiFlaaLI1WWoare bth a to 0,the folow gplesforXN being and1t

mvLXSbCol[ xSbldx31[ySbldx ]=ctrMvLX (8-590)

predFlagLXSbCollxSbdx][ySbtdx)=ctrPred lagLX (8-591)

gbildxbbCol [xSbtdx ][ySbldx]=ctrgidx (x-xxx)

[2041 12051 [Table 10]

8.4A.4 Deivtion proiss for sablock-Iased temporaltmergingbase motion data

Inputsto this processor: - the location (xCthyCtbo oftie top-ieft sample oftheluma coding tree blockdthtcontains the current coding block, - the location (xColCirCb, ColCtrCb )of the top-letsample ofthe collocated luma codng blck that coers thehbelow-right center sample.

- the availability flags availableFlagAs, axailableFlagAi. availableFlagls and axailableFlag~i of the neighboring coding units, - the reference indices refldxLXAs, reffldxLXAi refldxLXBoand refldxLXti ofthe neighbouring coding unit,

- the prediction list tizaon flags predFlagLXAopredFlaLXA predFlagLXBandpredFlagLXBiofthe neighbouring coding units, - themotionvectorsin116fractional-sampleaccuracymvLXAg, mvLXBo, -LXA andm-LXiof the neighbouring coding unts. Outputs ofthis processare

- themotion vectorsctrMvLOandtrMvL1 - the prediction list utilization flagstrPredFlagL andtrPredFlagL1L - the reference indices crRefldxLOand trRefldxL1,

- the temporal motion vector temnpMV,

- thehbi-prediction weight index trgbildx. The variable tempMv is set as follows:

tesmpMy[ 0-= 0 (8-592)

tempMv[l =0 (8-593)

Thevarisable currPc specifies the current picture.

Thexiariableax alableFlagNis set equal to FASEa:mdthefollowingippliew -Whenav~ailableFlagAiisequalto1. thef:ollowing applies - ailabeagisset equal toTRUE,

- refldxLXN is set equalto re d xLA5 d :tXNi s e teuto in :ngeplaedby gA

- W aailableFlagN isaequalto ALSE ndaaiAbleFlagL is equal to 1 thefollowing applies: - availableagNisset equal to TRUE, - refldxLXN is set equal tomrfldxLXEo and mvLXN is set equal to mvLXBe for Xbeing replaced by o and L When avadableagNisequaltoFAlSE adavaIableFlagi tthefollowigapplies: - availableFlagNis setequaltoTRUE. - re~dxLN isset equal to refidxLXB and mvLXN is set equal tomvLXBL for Xbeing replaced by

- When avadlableFlagNis equal toFALSE and available~lagAis equal to1, the following applies: - availableFlaN isset equal to TRUE - reff dLN is set equal to raffdxLA andusvLNisset equa tosnvLXA for Xbe mreplac ed by O and 1 When available~lagN is equal to TRUE, the following applies: - If all of the following conditions are true, tempMV is set equal to mvL iN:

- prdFlagLNis equal to 1, - DiffPicOrderCnt(ColPicRePcListileIdxLIN]) isequal to 0, - DiffPicOrdernt(aPie, crPie)is less thnorequal to Ofor every p wemSP i ine'o te e fenc pictures tofth current tile group, - ilegroup_type is equalto

- collocated_from_10flag is equal to0.

[2061 - Otherwise if all of the following conditions are true, temspMVis st eqal tosL - ped aLONis equal toL1

- DiffPicOrderCat(ColPie, RefPieListolrefldxL0N])iseqsual to0. The location (xColCbyColCb )ofthe collocated block inside CoPic is derived asfollows.

xColChb=Clip3( xCth, Min( CurPicWidthlnSamnplesY - 1, xCtb +(I 1 «CtbLog2SizeY ) +3)(8-59 4) xColCrCb + (tempMV[0 »4j) )

ycolc = Clip3( yCtb, Min( CurPic-eightlnSamsplesY -1, yCtb +( 1< «CtbLog2SizeY ) -1 ),(8-5 95) yColCtrCb + (tempMv]» 4 ))

The array colPredMde is set equal to th prediction mode array CoPredMode of te ollocaedp ar specified by ColPie. The motion vectors ctrMvLO and cMr11.th preditionlist utlizationflags ctrPred~lagL0 ad ctrPredlagt l and the referenceindics tiRe30 nd rtrRefldxl1are denied afiows: - If coiPredModedxColCb][yColCb] sito0MODEINT ER thefolowngappies - Thevariable currabsecifiesthe lumnacodingblock coverng CtrUbyCb insidee thecurrent picture. -ThevariablecolCbhspecifwestheunascoding blockcoverngthe modified location gvnby

[2071 ((N° 3(***°>) *3 )nsdeh Noi

-The luma location (xColCb, yColCb )istsetequa to the top-ien sapieof the collocated luma coding block specifed bycolCb relative to the top-leftium sapieof the collocated picture specified byColPic. - The gbildx5bCol is set equal tetrgbildx - The derivationprocessfor temporal motion vector predictionin subclause 8.4212isinvokedwith currCb eu!Cb, (ColCb, yColCb),centerRetldLO andbFlag set equal o Iasinputs and the output beingassined toctrMvLO andctrPredflagmtl - The derivation processfor tmpora moinn ectorpredicionimnsubclause S.4l.2is moked t currCb colCb, (xColCb.-ColCb, center eiaL1.and sbFlag set equal to 1asinputs andth outputbteingasgned toctrM'LI adetPredlagLi. - Othervises the following applies: ctPredFlagLO = 0 (8-596)

ctrPredFlagtL1 -0 (8-597)

[2081

[2091 Referring to Table 8, Table 9, and Table 10, gbidx may indicate abi-prediction weight

index, and gbildxSbCol may indicate abi-prediction weight index for asubblock-based

candidate list). In the procedure (8.4.4.3) for deriving base motion information on subblock

based temporal merge, the gbildxSbCol may be derived as gbidxcolCb. Alternatively, in the

procedure (8.4.4.3) of deriving base motion information onsubblock-based temporal merge

according to acondition (eg, when availableFlagLOSbCol and availableFlagL1SbCol are both

), the gbildxSbCol may be derived as ctrgbildx, and in the procedure (8.4.4.4) for deriving

base motion information on subblock-based temporal merge, the ctrgbildx may be derived as

gbildxSbCol. That is, the weight index ofthe subblock-based temporal motion vector

candidate may be derived as aweight index in units of each subblock, or when the subblock is

not available, may be derived as the weight index of the temporal center block. For example,

of the four central subblocks or samples of the col block or asample.

[210] Meanwhile, according toanother embodiment of the present disclosure, when

constructing amotion vector candidate for amerge mode, weight index information on apair wise candidate may be derived. For example, a pair-wise candidate may be included in the merge candidate list, and weight index information on a weighted average of the pair-wise candidate may be derived. The pair-wise candidate may be derived based on other merge candidates in the merge candidate list, and when the pair-wise candidate uses bi-prediction, a weight index for a weighted average may be derived. That is, when the inter-prediction type is bi-prediction, weight index information on pair-wise candidates in the merge candidate list may be derived.

[211] The pair-wise candidate may be derived based on other two merge candidates (eg,

candO and candle) among the candidates included in the merge candidate list.

[212] For example, the weight index information on the pair-wise candidate may be derived

based on the weight index information on any one of the two merge candidates (eg, the merge

candidate cand or the merge candidate candle . For example, the weight index information

on the pair-wise candidate may be derived based on the weight index information on a

candidate using bi-prediction among the two merge candidates.

[213] Alternatively, when the weight index information on each of the other two merge

candidates is the same as the first weight index information, the weight index information on

the pair-wise candidate may be derived based on the first weight index information.

Meanwhile, when the weight index information on each of the other two merge candidates is

not the same, the weight index information on the pair-wise candidate may be derived based

on the default weight index information. The default weight index information may

correspond to weight index information on assignment of the same weight to each of the LO

prediction samples and the Li prediction samples.

[214] Alternatively, when the weight index information on each of the other two merge

not the same, the weight index information on the pair-wise candidate includes the default

weight index information among the weight index information on each of the other two

candidates. The default weight index information may correspond to weight index

information on assignment of the same weight to each of the LO prediction samples and the LI

prediction samples.

[215] Meanwhile, according to another embodiment of the present disclosure, when

constructing a motion vector candidate for a merge mode in units of subblocks, weight index

information on a weighted average of temporal motion vector candidates may be derived.

Here, the merge mode in units of subblocks may be referred to as an affine merge mode (in

units of subblocks). The temporal motion vector candidate may indicate a subblock-based

temporal motion vector candidate, and may be referred to as an SbTMVP (or ATMVP)

candidate. The weight index information on the SbTMVP candidate may be derived based

on the weight index information on the left neighboring block of the current block. That is,

when the candidate derived by SbTMVP uses bi-prediction, the weight index of the left

neighboring block of the current block may be derived as the weight index for the subblock

based merge mode.

[216] For example, since the SbTMVP candidate may derive a col block based on the

spatially adjacent left block (or left neighboring block) of the current block, the weight index

of the left neighboring block may be considered reliable. Accordingly, the weight index for

the SbTMVP candidate may be derived as the weight index of the left neighboring block.

[217] Meanwhile, according to another embodiment of the present disclosure, when

constructing a motion vector candidate for an affine merge mode, in the case where an affine

merge candidate uses bi-prediction, weight index information on a weighted average may be

derived. That is, when the inter-prediction type is bi-prediction, weight index information on a candidate in the affine merge candidate list or the subblock merge candidate list may be derived.

[218] For example, among affine merge candidates, a constructed affine merge candidate

may derive CPO, CP1, CP2, or CP3 candidatesbased on a spatially adjacentblock of the current

block or a temporally adjacent block to indicate a candidate for deriving the MVF as the affine

model. For example, CPO may indicate a control point located at the upper-left sample

position of the current block, CP 1 may indicate a control point located at the upper-right sample

position of the current block, and CP2 may indicate the bottom-left sample position of the

current block. Also, CP3 may indicate a control point located at the bottom-right sample

position of the current block.

[219] For example, among the affine merge candidates, the constructed affine merge

candidates may be generated based on a combination of each control point like {CPO, CP1,

CP2}, {CPO,CP1,CP3}, {CPO,CP2, CP3}, {CP1,CP2,CP3}, {CPO,CP1}, and {CPO, CP2}

may be generated based on a combination of each control point of the current block. For

example, the affine merge candidates may include at least one of{CPMVO, CPMV1, CPMV2},

{CPMVO, CPMV1, CPMV3}, {CPMVO, CPMV2, CPMV3}, {CPMV1, CPMV2, CPMV3},

{CPMVO, CPMV1}, and {CPMVO, CPMV2 }. CPMVO, CPMV1, CPMV2, and CPMV3

may correspond to motion vectors for CPO, CP1, CP2, and CP3, respectively.

[220] In an embodiment, when the affine merge candidate includes a CPMV for control point

(CPO) positioned at the top-left of the current block, the weight index information on the

affine merge candidate may be derived based on weight index information on a specific block

among neighboring blocks of the CPO. That is, when the affine merge candidate includes a

CPMV for control point 0 (CPO) positioned at the top-left of the current block, the weight index

information on the affine merge candidate may be derived based on 0 th weight index

information on the CPO. In this case, a specific block among the neighboring blocks of CPO corresponds to the block used for derivation of CPMV for the CPO, and the neighboring blocks of CPO may include the top-left corner neighboring block of the current block, the left neighboring block adjacent to the bottom of the top-left corner neighboring block, and the upper neighboring block adjacent to the right of the top-left corner neighboring block.

[221] On the other hand, when the affine merge candidate does not include a CPMV for CPO

positioned at the top-left of the current block, the weight index information on the affine merge

candidate may be derived based on weight index information on a specific block among

neighboring blocks of control point 1 (CP1) positioned at the top-right position of the current

block. That is, when the affine merge candidate does not include a CPMV for CPO positioned

at the top-left of the current block, the weight index information on the affine merge candidate

may be derived based on the first weight index information for control point 1 (CP1) located

at the top-right of the current block. Among the neighboring blocks of the CP1, a specific

block corresponds to the block used for derivation of the CPMV for the CP1, and the CP

neighboring blocks may include the top-right corner neighboring block of the current block

and the top neighboring block adjacent to the left of the top-right corner neighboring block.

[222] According to the above method, the weight index information on the affine merge

candidate may be derived based on weight index information of a block used for deriving

{CPMVO, CPMV1, CPMV2}, {CPMVO1, CPMV1, CPMV3}, {CPMVO, CPMV2, CPMV3},

{CPMV1, CPMV2, CPMV3}, {CPMVO, CPMVI} and {CPMVO, CPMV2}, respectively.

[223] According to another embodiment of deriving the weight index information on the

affine merge candidate, when the weight index information for CPO positioned at the top-left

of the current block and the weight index information on CP1 positioned at the top-right of the

current block are the same, the weight index information on the affine merge candidate may be

derived based on weight index information on a specific block among neighboring blocks of

the CPO. Meanwhile, when the weight index information on the CPO positioned at the top left of the current block and the weight index information on the CP Ipositioned at the top right of the current block are not the same, the weight index information on the affine merge candidate may be derived based on default weight index information. The default weight index information may correspond to weight index information on giving the same weight to each of the LO prediction samples and the L prediction samples.

[224] According to another embodiment of deriving the weight index information on the

affine merge candidate, the weight index information on the affine merge candidate may be

derived as a weight index of a candidate having a high frequency of occurrence among the

weight indexes of each candidate. For example, a weight index of a candidate block

determined as a motion vector in CPO among CPO candidate blocks, a weight index of a

candidate block determined as a motion vector in CP1 among CP1 candidate blocks, a weight

index of a candidate block determined as a motion vector in CP2 among CP2 candidate blocks,

and/or the most overlapping weight index among the weight indexes of the candidate blocks

determined as the motion vector in CP3 among the CP3 candidate blocks may be derived as

the weight index of the affine merge candidate.

[225] For example, CPO and CP1 maybe used as the control point, CPO, CP1, and CP2 may

be used, and CP3 may not be used. However, for example, when a CP3 candidate of an affine

block (a block coded in the affine prediction mode) is to be used, the method of deriving a

weight index in the temporal candidate block described in the above-described embodiments

may be used.

[226] FIGS. 10 and 11 are diagrams schematically illustrating an example of a video/image

[227] The method disclosed in FIG. 10 may be performed by the encoding apparatus

disclosed in FIG. 2 or 11. Specifically, for example, S1000 to S1030 of FIG. 10 may be

performed by the predictor 220 of the encoding apparatus 200 in FIG. 11, and S1040 of FIG.

may be performed by an entropy encoder 240 of the encoding apparatus 200 in FIG. 11.

In addition, although not illustrated in FIG. 10, in FIG. 11, prediction samples or prediction

related information may be derived by the predictor 220 of the encoding apparatus 200, residual

information may be derived from original samples or prediction samples by the residual

processor 230 of the encoding apparatus 200, and a bitstream may be generated from residual

information or prediction-related information by the entropy encoder 240 of the encoding

apparatus 200 . The method disclosed in FIG. 10 may include the embodiments described

above in the present disclosure.

[228] Referring to FIG. 10, the encoding apparatus may determine the inter-prediction mode

of the current block and generate inter-prediction mode information indicating the inter

prediction mode (S1000). For example, the encoding apparatus may determine a merge mode,

an affine (merge) mode, or a subblock merge mode as an inter-prediction mode to be applied

to the current block, and may generate inter-prediction mode information indicating the

determined merge mode, affine (merge) mode, or subblock merge mode.

[229] The encoding apparatus may generate a merge candidate list of the current block based

on the inter-prediction mode (Sl100). For example, the encoding apparatus may generate a

merge candidate list according to the determined inter-prediction mode. Here, when the

determined inter-prediction mode is an affine merge mode or a subblock merge mode, the

merge candidate list may be referred to as an affine merge candidate list or a subblock merge

candidate list, but may also be simply referred to as a merge candidate list.

[230] For example, candidates may be inserted into the merge candidate list until the number

of candidates in the merge candidate list becomes the maximum number of candidates. Here,

the candidate may indicate a candidate or a candidate block for deriving motion information

(or motion vector) of the current block. For example, the candidate block may be derived

through a search for neighboring blocks of the current block. For example, a neighboring block may include a spatial neighboring block and/or a temporal neighboring block of the current block, a spatial neighboring block may be preferentially searched to derive a (spatial merge) candidate, and then a temporal neighboring block may be searched to derive a (temporal merge) candidate, and the derived candidates may be inserted into the merge candidate list.

For example, when the number of candidates in the merge candidate list is less than the

maximum number of candidates in the merge candidate list even after the candidates are

inserted, additional candidates may be inserted. For example, additional candidates include

at least one of history based merge candidate(s), pair-wise average merge candidate(s), ATMVP,

and combined bi-predictive merge candidates (when the slice/tile group type of the current

slice/tile group is type B) and/or a zero vector merge candidate.

[231] Alternatively, for example, candidates may be inserted into the affine merge candidate

list until the number of candidates in the affine merge candidate list becomes the maximum

number of candidates. Here, the candidate may include a control point motion vector (CPMV)

of the current block. Alternatively, the candidate may indicate a candidate or a candidate

block for deriving the CPMV. The CPMV may indicate a motion vector at a control point

(CP) of the current block. For example, the number of CPs may be 2, 3, or 4, the CP may be

positioned at at least a part of top-left (or top-left corner), top-right (or top-right corner),

bottom-left (or bottom-left corner), or bottom-right (or bottom-right corner) of the current

block, and only one CP may exist at each position.

[232] For example, a candidate may be derived through a search for a neighboring block (or

a neighboring block of a CP of the current block) of the current block. For example, the affine

merge candidate list may include at least one of an inherited affine merge candidate, a

constructed affine merge candidate, and a zero motion vector candidate. For example, in the

affine merge candidate list, the inherited affine merge candidate may be inserted first, and then

the constructed affine merge candidate maybe inserted. In addition, even though affine merge candidates constructed in the affine merge candidate list are inserted, when the number of candidates in the affine merge candidate list is smaller than the maximum number of candidates, the remainder maybe filled with zero motion vector candidates. Here, the zero motion vector candidate may be referred to as a zero vector. For example, the affine merge candidate list may be a list according to an affine merge mode in which a motion vector is derived in units of samples, or may be a list according to an affine merge mode in which a motion vector is derived in units of subblocks. In this case, the affine merge candidate list may be referred to as a subblock merge candidate list, and the subblock merge candidate list may also include candidates (or SbTMVP candidates) derived from SbTMVP. For example, when the

SbTMVP candidate is included in the subblock merge candidate list, it may be positioned

before the inherited affine merge candidate and the constructed affine merge candidate in the

subblock merge candidate list.

[233] The encoding apparatus may generate selection information indicating one of

candidates included in the merge candidate list (S1020). For example, the merge candidate

list may include at least some of a spatial merge candidate, a temporal merge candidate, a pair

wise candidate, or a zero vector candidate, and one of these candidates may be selected for

inter-prediction of the current block. Alternatively, for example, the subblock merge

candidate list may include at least some of an inherited affine merge candidate, a constructed

affine merge candidate, an SbTMVP candidate, or a zero vector candidate, and one candidate

of these candidates for inter-prediction of the current block may be selected.

[234] For example, the selection information may include index information indicating a

selected candidate in the merge candidate list. For example, the selection information may be

referred to as merge index information or subblock merge index information.

[235] The encoding apparatus may generate inter-prediction type information indicating the

inter-prediction type of the current block as the bi-prediction (S1030). For example, the inter prediction type of the current block may be determined as bi-prediction among LO prediction,

LI prediction, or bi-prediction, and inter-prediction type information indicating this may be

generated. Here, LO prediction may indicate prediction based on reference picture list 0, LI

prediction may indicate prediction based on reference picture list 1, and bi-prediction may

indicate prediction based on reference picture list 0 and reference picture list 1. For example,

the encoding apparatus may generate inter-prediction type information based on the inter

prediction type. For example, the inter-prediction type information may include an

interpredidc syntax element.

[236] The encoding apparatus may encode image information including inter-prediction

mode information, selection information, and inter-prediction type information (S1040). For

example, the image information may be referred to as video information. The image

information may include various information according to the above-described embodiment(s)

of the present disclosure. For example, the image information may include at least a part of

prediction-related information or residual-related information. For example, the prediction

related information may include at least a part of the inter-prediction mode information,

selection information, and inter-prediction type information. For example, the encoding

apparatus may generate a bitstream or encoded information by encoding image information

including all or part of the above-described information (or syntax elements). Alternatively,

it may be output in the form of a bitstream. In addition, the bitstream or encoded information

may be transmitted to the decoding apparatus through a network or a storage medium.

[237] Although not illustrated in FIG. 10, for example, the encoding apparatus may generate

prediction samples of the current block. Alternatively, for example, the encoding apparatus

may generate prediction samples of the current block based on the selected candidate.

Alternatively, for example, the encoding apparatus may derive motion information based on

the selected candidate, and may generate prediction samples of the current block based on the motion information. For example, the encoding apparatus may generate LO prediction samples and LI prediction samples according to bi-prediction, and may generate prediction samples of a current block based on the LO prediction samples and the L prediction samples.

In this case, prediction samples of the current block may be generated from the LO prediction

samples and the Li prediction samples using weight index information (or weight information)

for bi-prediction. Here, the weight information may be displayed based on the weight index

information.

[238] In other words, for example, the encoding apparatus may generate LO prediction

samples and Li prediction samples of the current block based on the selected candidate. For

example, when the inter-prediction type of the current block is determined to be bi-prediction,

the reference picture list 0 and the reference picture list 1 may be used for prediction of the

current block. For example, the LO prediction samples may represent prediction samples of

the current block derived based on the reference picture list 0, and the L prediction samples

may represent prediction samples of the current block derived based on the reference picture

list 1.

[239] For example, the candidates may include a spatial merge candidate. For example,

when the selected candidate is the spatial merge candidate, LO motion information and LI

motion information may be derived based on the spatial merge candidate, and the LO prediction

samples and the Li prediction samples are generated based thereon.

[240] For example, the candidates may include a temporal merge candidate. For example,

when the selected candidate is the temporal merge candidate, LO motion information and LI

motion information may be derived based on the temporal merge candidate, and the LO

prediction samples and the Li prediction samples are generated based thereon.

[241] For example, the candidates may include pair-wise candidates. For example, when

the selected candidate is a pair-wise candidate, LO motion information and LI motion information may be derived based on the pair-wise candidate, and the LO prediction samples and the L prediction samples may be generated based thereon. For example, the pair-wise candidate may be derived based on two other candidates among the candidates included in the merge candidate list.

[242] Alternatively, for example, the merge candidate list may be a subblock merge

candidate list, and an affine merge candidate, a subblock merge candidate, or an SbTMVP

candidate may be selected. Here, the affine merge candidate in units of subblocks may be

referred to as a subblock merge candidate.

[243] For example, the candidates may include a subblock merge candidate. For example,

when the selected candidate is the subblock merge candidate, LO motion information and LI

motion information may be derived based on the subblock merge candidate, and the LO

prediction samples and the LI prediction samples are generated based thereon. Forexample,

the subblock merge candidate may include control point motion vectors (CPMVs), and the LO

prediction samples and the Li prediction samples may be generated by performing prediction

in units of subblock based on the CPMVs.

[244] Here, the CPMV may be indicated based on one block among neighboring blocks of a

control point (CP) of the current block. For example, the number of CPs may be 2, 3, or 4,

the CP may be positioned at at least a part of top-left (or top-left corner), top-right (or top-right

corner), bottom-left (or bottom-left corner), or bottom-right (or bottom-right corner) of the

current block, and only one CP may exist at each position.

[245] For example, the CP may be CPO positioned at the top-left of the current block. In

this case, the neighboring blocks may include a top-left corner neighboring block of the current

block, a bottom-left neighboring block adjacent to the bottom of the top-left corner neighboring

block, and a top neighboring block adjacent to the right of the top-left corner neighboring block.

Alternatively, the neighboring blocks may include an A 2 block, a B 2 block, or a B 3 block in

FIG. 8.

[246] Alternatively, for example, the CP may be CP 1 positioned at the top-right of the current

block. In this case, the neighboring blocks may include a top-right corner neighboring block

of the current block and a top neighboring block adjacent to the left of the top-right corner

neighboring block. Alternatively, the neighboring blocks may include a Bo block or a Bi

block in FIG. 8.

[247] Alternatively, for example, the CP may be CP2 positioned at the bottom-left of the

current block. In this case, the neighboring blocks may include the bottom-left corner

neighboring block of the current block and the left neighboring block adjacent to the top of the

bottom-left corner neighboring block. Alternatively, the neighboring blocks may include the

Ao block or the Ai block in FIG. 8.

[248] Alternatively, for example, the CP may be a CP3 positioned at the bottom-right of the

current block. Here, CP3 may also be referred to as RB. In this case, the neighboring blocks

may include a col block of the current block or a bottom-right corner neighboring block of the

collocated block. Here, the collocated block may include a block at the same position as the

current block in a reference picture different from the current picture in which the current block

is positioned. Alternatively, the neighboring block may include block T in FIG. 8.

[249] Alternatively, for example, the candidates may include SbTMVP candidates. For

example, when the selected candidate is the SbTMIVP candidate, the LO motion information

and the LI motion information may be derived based on the left neighboring block of the

current block, and based on this, the LO prediction samples and the L prediction samples may

begenerated. For example, the LO prediction samples and the LI prediction samples maybe

generated by performing prediction in units of subblocks.

[250] For example, the LO motion information may include an LO reference picture index,

an LO motion vector, and the like, and the LI motion information may include an LI reference picture index, an LI motion vector, and the like. The LO reference picture index may include information indicating the reference picture in the reference picture list 0, and the L reference picture index may include information indicating the reference picture in the reference picture list 1.

[251] For example, the encoding apparatus may generate prediction samples of the current

block based on LO prediction samples, L prediction samples, and weight information. For

example, the weight information may be displayed based on the weight index information.

The weight index information may indicate weight index information on bi-prediction. For

example, the weight information may include information on a weighted average of LO

prediction samples or LI prediction samples. That is, the weight index information may

indicate index information on a weight used for the weighted average, and may generate weight

index information in a procedure of generating prediction samples based on the weighted

average. For example, the weight index information may include information indicating any

one of three or five weights. For example, the weighted average may represent a weighted

average in bi-prediction with CU-level weight (BCW) or bi-prediction with weighted average

(BWA).

[252] For example, the candidates may include a temporal merge candidate, and the weight

index information on the temporal merge candidate may be represented by 0. That is, the

weight index information on the temporal merge candidate may be represented by 0. Here,

the weight index information of 0 may mean that the weights of each reference direction (ie,

the LO prediction direction and the LI prediction direction in bi-prediction) are the same.

Alternatively, for example, the candidates may include a temporal merge candidate, and the

weight index information may be indicated based on weight index information on a col block.

That is, the weight index information on the temporal merge candidate may be indicated based

on the weight index information on the col block. Here, the collocated block may include a block at the same position as the current block in a reference picture different from the current picture in which the current block is positioned.

[253] For example, the candidates may include a pair-wise candidate, and the weight index

information may be indicated based on weight index information on one of the other two

candidates in the merge candidate list used to derive the pair-wise candidate. That is, the

weight index information on the pair-wise candidate may be indicated based on the weight

index information on one of the other two candidates in the merge candidate list used to derive

the pair-wise candidate.

[254] For example, the candidates may include the pair-wise candidate, and the pair-wise

candidate may be indicated based on other two candidates among the candidates. When the

weight index information on each of the other two candidates is the same as the first weight

index information, the weight index information on the pair-wise candidate may be indicated

based on the first weight index information, When the weight index information on each of the

other two candidates is not the same, the weight index information on the pair-wise candidate

may be indicated based on default weight index information, and In this case, the default weight

index information may correspond to weight index information on giving the same weight to

each of the LO prediction samples and the L prediction samples.

[255] For example, the candidates may include the pair-wise candidate, and the pair-wise

based on the first weight index information. When the weight index information on each of

the other two candidates is not the same, the weight index information may be indicated based

on weight index information rather than the default weight index information among the weight

index information of each of the other two candidates. The default weight index information may correspond to weight index information on giving the same weight to each of the LO prediction samples and the Li prediction samples.

[256] For example, the merge candidate list may be a subblock merge candidate list, and an

affine merge candidate, a subblock merge candidate, or an SbTMVP candidate may be selected.

Here, the affine merge candidate in units of subblocks may be referred to as a subblock merge

candidate.

[257] For example, the candidates include an affine merge candidate, and the affine merge

candidate may include control point motion vectors (CPMVs).

[258] For example, when the affine merge candidate includes a CPMV for control point 0

(CPO) positioned in the top-left of the current block, the weight index information on the affine

merge candidate may be indicated based on weight index information on a specific block

among neighboring blocks of the CPO. When the affine merge candidate does not include a

CPMV for CPO positioned at the top-left of the current block, the weight index information on

the affine merge candidate may be indicated based on weight index information on a specific

block among neighboring blocks of control point 1 (CP1) positioned in the top-right position

of the current block.

[259] A specific block among the neighboring blocks of CPO corresponds to the block used

for derivation of CPMV for the CPO, and the neighboring blocks of CPO may include the top

left corner neighboring block of the current block, the left neighboring block adjacent to the

bottom of the top-left corner neighboring block, and the top neighboring block adjacent to the

right of the top-left corner neighboring block.

[260] Among the neighboring blocks of the CP1, a specific block corresponds to the block

used for derivation of the CPMV for the CP1, and the CP Ineighboring blocks may include the

top-right corner neighboring block of the current block and the top neighboring block adjacent

to the left of the top-right corner neighboring block.

[261] Alternatively, for example, the candidates may include an SbTMVP candidate, and

weight index information on the SbTMVP candidate may be indicated based on weight index

information on a left neighboring block of the current block. That is, the weight index

information on the SbTMVP candidate may be indicated based on the weight index information

on the left neighboring block.

[262] Alternatively, for example, the candidates may include the SbTMVP candidate, and

weight index information on the SbTMVP candidate may be represented by 0. That is, the

weight index information on the SbTMVP candidate may be represented by 0. Here, the

weight index information of 0 may mean that the weights of each reference direction (ie, the

LO prediction direction and the Li prediction direction in bi-prediction) are the same.

[263] Alternatively, for example, the candidates may include the SbTMVP candidate, and

the weight index information may be indicated based on weight index information on a center

block in a col block. That is, the weight index information on the SbTMVP candidate may

be indicated based on the weight index information on the center block in the col block. Here,

the collocated block may include a block at the same position as the current block in a reference

picture different from the current picture in which the current block is positioned, and the center

block may include a bottom-right subblock among four subblocks located in the center of the

collocated block.

[264] Alternatively, for example, the candidates may include the SbTMVP candidate, and

the weight index information may be indicated based on weight index information on each of

the subblocks in a col block. That is, the weight index information on the SbTMVP candidate

may be indicated based on the weight index information on each of the subblocks of the col

block.

[265] Alternatively, although not illustrated in FIG. 10, for example, the encoding apparatus

may derive residual samples based on the prediction samples and original samples. In this case, the residual-related information may be derived based on the residual samples. The residual samples maybe derived based on the residual-related information. The reconstructed samples may be generated based on the residual samples and the prediction samples. A reconstructed block and a reconstructed picture may be derived based on the reconstructed samples. Alternatively, for example, the encoding apparatus may encode image information including residual-related information or prediction-related information.

[266] For example, the encoding apparatus may generate a bitstream or encoded information

by encoding image information including all or part of the above-described information (or

syntax elements). Alternatively, it may be output in the form of a bitstream. In addition, the

bitstream or encoded information may be transmitted to the decoding apparatus through a

network or a storage medium. Alternatively, the bitstream or the encoded information may

be stored in a computer-readable storage medium, and the bitstream or the encoded information

may be generated by the above-described image encoding method.

[267] FIGS. 12 and 13 are diagrams schematically illustrating an example of a video/image

[268] The method disclosed in FIG. 12 may be performed by a decoding apparatus disclosed

in FIG. 3 or 13. Specifically, for example, S1200 of FIG. 12 may be performed by an entropy

decoder 310 of a decoding apparatus 300 in FIG. 13, and S1210 to S1260 of FIG. 12 are

performed a predictor 330 of the decoding apparatus 300 in FIG. 13. Also, although not

illustrated in FIG. 12, in FIG. 13, prediction-related information or residual information may

be derived from a bitstream by the entropy decoder 310 of the decoding apparatus 300, residual

samples may be derived from residual information by the residual processor 320 of the

decoding apparatus 300, prediction samples may be derived from prediction-related

information by the predictor 330 of the decoding apparatus 300, and a reconstructed block or

a reconstructed picture may be derived from residual samples or prediction samples by an adder

340 of the decoding apparatus 300. The method disclosed in FIG. 12 may include the

embodiments described above in the present disclosure.

[269] Referring to FIG. 12, the decoding apparatus may receive image information including

inter-prediction mode information and inter-prediction type information through a bitstream

(S1200). For example, the image information maybe referred to as video information. The

image information may include various information according to the above-described

embodiment(s) of the present disclosure. For example, the image information may include at

least a part of prediction-related information or residual-related information.

[270] For example, the prediction-related information may include inter-prediction mode

information or inter-prediction type information. For example, the inter-prediction mode

information may include information indicating at least some of various inter-prediction modes.

For example, various modes such as a merge mode, a skip mode, a motion vector prediction

(MVP) mode, an affine mode, a subblock merge mode, or a merge with MVD (MMVD) mode

may be used. In addition, a decoder side motion vector refinement (DMVR) mode, an

adaptive motion vector resolution (AMVR) mode, a bi-prediction with CU-level weight, or a

bi-directional optical flow (BDOF), etc. may be used in addition or instead as ancillary mods.

For example, the inter-prediction type information may include an interpredide syntax

element. Alternatively, the inter-prediction type information may include information

indicating any one of LO prediction, L prediction, and bi-prediction.

[271] The decoding apparatus may generate a merge candidate list of the current block based

on the inter-prediction mode information (S1210). For example, the decoding apparatus may

determine the inter-prediction mode of the current block as a merge mode, an affine (merge)

mode, or a subblock merge mode based on the inter-prediction mode information, and generate

a merge candidate list according to the determined inter-prediction mode. Here, when the

inter-prediction mode is an affine merge mode or a subblock merge mode, the merge candidate list may be referred to as an affine merge candidate list or a subblock merge candidate list, but may also be simply referred to as a merge candidate list.

[272] For example, candidates may be inserted into the merge candidate list until the number

through a search for neighboring blocks of the current block. For example, a neighboring

block may include a spatial neighboring block and/or a temporal neighboring block of the

current block, a spatial neighboring block may be preferentially searched to derive a (spatial

merge) candidate, and then a temporal neighboring block may be searched to derive a (temporal

merge) candidate, and the derived candidates may be inserted into the merge candidate list.

slice/tile group is type B) and/or a zero vector merge candidate.

[273] Alternatively, for example, candidates may be inserted into the affine merge candidate

bottom-left (or bottom-left corner), or bottom-right (or bottom-right corner) of the current block, and only one CP may exist at each position.

[274] For example, a candidate block may be derived through a search for a neighboring

block (or a neighboring block of a CP of the current block) of the current block. For example,

the affine merge candidate list may include at least one of an inherited affine merge candidate,

a constructed affine merge candidate, and a zero motion vector candidate. For example, in

the affine merge candidate list, the inherited affine merge candidate may be inserted first, and

then the constructed affine merge candidate may be inserted. In addition, even though affine

merge candidates constructed in the affine merge candidate list are inserted, when the number

of candidates in the affine merge candidate list is smaller than the maximum number of

candidates, the remainder may be filled with zero motion vector candidates. Here, the zero

motion vector candidate may be referred to as a zero vector. For example, the affine merge

candidate list may be a list according to an affine merge mode in which a motion vector is

derived in units of samples, or may be a list according to an affine merge mode in which a

motion vector is derived in units of subblocks. In this case, the affine merge candidate list

may be referred to as a subblock merge candidate list, and the subblock merge candidate list

may also include candidates (or SbTMVP candidates) derived from SbTMVP. For example,

when the SbTMVP candidate is included in the subblock merge candidate list, it may be

positioned before the inherited affine merge candidate and the constructed affine merge

candidate in the subblock merge candidate list.

[275] The decoding apparatus may generate selection information indicating one of

candidates included in the merge candidate list (S1220). For example, the merge candidate

candidate list may include at least some of an inherited affine merge candidate, a constructed affine merge candidate, an SbTMVP candidate, or a zero vector candidate, and one candidate of these candidates for inter-prediction of the current block may be selected. For example, the selected candidate may be selected from the merge candidate list based on selection information. For example, the selection information may include index information indicating a selected candidate in the merge candidate list. For example, the selection information may be referred to as merge index information or subblock merge index information. For example, the selection information may be included in the image information. Alternatively, the selection information may be included in the inter-prediction mode information.

[276] The decoding apparatus may derive the inter-prediction type of the current block as bi

prediction based on the inter-prediction type information (S1230). For example, the inter

prediction type of the current block may be derived as bi-prediction among LO prediction, LI

prediction, or bi-prediction based on the inter-prediction type information. Here, LO

prediction may indicate prediction based on reference picture list 0, L prediction may indicate

prediction based on reference picture list 1, and bi-prediction may indicate prediction based on

reference picture list 0 and reference picture list 1. For example, the inter-prediction type

information may include an interpredide syntax element.

[277] The decoding apparatus may derive motion information on the current block based on

the selected candidate (S1240). For example, the decoding apparatus may derive LO motion

information and Li motion information based on a candidate selected as the inter-prediction

type is derived as bi-prediction. For example, the LO motion information may include an LO

reference picture index, an LO motion vector, and the like, and the L motion information may

include an LI reference picture index, an LI motion vector, and the like. The LO reference

picture index may include information indicating the reference picture in the reference picture

list 0, and the L reference picture index may include information indicating the reference picture in the reference picture list 1.

[278] The decoding apparatus may generate LO prediction samples and LI prediction

samples of the current block based on the motion information (S1250). Forexample,when

the inter-prediction type of the current block is derived as bi-prediction, the reference picture

list 0 and the reference picture list 1 may be used for prediction of the current block. For

example, the LO prediction samples may represent prediction samples of the current block

derived based on the reference picture list 0, and the L prediction samples may represent

prediction samples of the current block derived based on the reference picture list 1.

[279] For example, the candidates may include a spatial merge candidate. For example,

samples and the Li prediction samples are generated based thereon.

[280] For example, the candidates may include a temporal merge candidate. For example,

prediction samples and the Li prediction samples are generated based thereon.

[281] For example, the candidates may include pair-wise candidates. For example, when

the selected candidate is a pair-wise candidate, LO motion information and LI motion

information may be derived based on the pair-wise candidate, and the LO prediction samples

and the L prediction samples may be generated based thereon. For example, the pair-wise

candidate may be derived based on two other candidates among the candidates included in the

merge candidate list.

[282] Alternatively, for example, the merge candidate list may be a subblock merge

candidate may be selected. Here, the affine merge candidate in units of subblocks may be referred to as a subblock merge candidate.

[283] For example, the candidates may include an affine merge candidate. For example,

when the selected candidate is the affine merge candidate, LO motion information and LI

motion information may be derived based on the affine merge candidate, and the LO prediction

samples and the LI prediction samples are generated based thereon. For example, the affine

merge candidate may include control point motion vectors (CPMVs), and the LO prediction

samples and the Li prediction samples may be generated by performing prediction in units of

subblock based on the CPMVs.

[284] Here, the CPMV may be derived based on one block among neighboring blocks of a

current block, and only one CP may exist at each position.

[285] For example, the CP may be CPO positioned at the top-left of the current block. In

Alternatively, the neighboring blocks may include an A2 block, a B2 block, or a B3 block in

FIG. 8.

[286] Alternatively, for example, the CP may be CP 1 positioned at the top-right of the current

neighboring block. Alternatively, the neighboring blocks may include a BO block or a B1

block in FIG. 8.

[287] Alternatively, for example, the CP may be CP2 positioned at the bottom-left of the current block. In this case, the neighboring blocks may include the bottom-left corner neighboring block of the current block and the left neighboring block adjacent to the top of the bottom-left corner neighboring block. Alternatively, the neighboring blocks may include the

Ao block or the Ai block in FIG. 8.

[288] Alternatively, for example, the CP may be a CP3 positioned at the bottom-right of the

[289] Alternatively, for example, the candidates may include SbTMVP candidates. For

generated by performing prediction in units of subblocks.

[290] For example, the decoding apparatus may generate prediction samples of the current

block based on LO prediction samples, LI prediction samples, and weight information (S1260).

For example, the weight information may be derived based on weight index information on a

candidate selected from among candidates included in the merge candidate list. For example,

the weight information may include information on a weighted average of LO prediction

samples orLi prediction samples. That is, the weight index information may indicate index

information on the weights used for the weighted average, and the weighted average may be

performed based on the weight index information. For example, the weight index information

may include information indicating any one of three or five weights. For example, the weighted average may represent a weighted average in bi-prediction with CU-level weight

(BCW) or bi-prediction with weighted average (BWA).

[291] For example, the candidates may include a temporal merge candidate, and the weight

index information on the temporal merge candidate may be derived as 0. That is, the weight

index information on the temporal merge candidate may be derived as 0. Here, the weight

index information of 0 may mean that the weights of each reference direction (ie, the LO

prediction direction and the Li prediction direction in bi-prediction) are the same.

[292] For example, the candidates may include a temporal merge candidate, and the weight

index information on the temporal merge candidate may be derived based on weight index

information on a col block. That is, the weight index information on the temporal merge

candidate may be derived based on the weight index information on the col block. Here, the

collocated block may include a block at the same position as the current block in a reference

picture different from the current picture in which the current block is positioned.

[293] For example, the candidates may include a pair-wise candidate, and the weight index

information may be derived as the weight index information on one of the other two candidates

in the merge candidate list used to derive the pair-wise candidate. That is, the weight index

information on the pair-wise candidate may be derived as the weight index information on one

of the other two candidates in the merge candidate list used to derive the pair-wise candidate.

[294] For example, the candidates may include the pair-wise candidate, and the pair-wise

candidate may be derived based on other two candidates among the candidates. When the

weight index information of each on the other two candidates is the same as the first weight

index information, the weight index information for the pair-wise candidate may be derived

the other two candidates is not the same, the weight index information on the pair-wise

candidate may be derived based on default weight index information, and In this case, the default weight index information may correspond to weight index information on giving the same weight to each of the LO prediction samples and the L prediction samples.

[295] For example, the candidates may include the pair-wise candidate, and the pair-wise

the other two candidates is not the same, the weight index information may be derived based

index information of each of the other two candidates. The default weight index information

may correspond to weight index information on giving the same weight to each of the LO

prediction samples and the Li prediction samples.

[296] For example, the merge candidate list may be a subblock merge candidate list, and an

candidate.

[297] For example, the candidates include an affine merge candidate, and the affine merge

candidate may include control point motion vectors (CPMVs).

[298] For example, when the affine merge candidate includes a CPMV for control point 0

merge candidate may be derived based on weight index information on a specific block among

neighboring blocks of the CPO. When the affine merge candidate does not include a CPMV

for CPO positioned at the top-left of the current block, the weight index information on the

among neighboring blocks of control point 1 (CP1) positioned in the top-right position of the current block.

[299] A specific block among the neighboring blocks of CPO corresponds to the block used

right of the top-left corner neighboring block.

[300] Among the neighboring blocks of the CP1, a specific block corresponds to the block

to the left of the top-right corner neighboring block.

[301] Alternatively, for example, the candidates may include an SbTMVP candidate, and

weight index information on the SbTMVP candidate may be derived based on weight index

information on the SbTMVP candidate may be derived based on the weight index information

on the left neighboring block.

[302] Alternatively, for example, the candidates may include the SbTMVP candidate, and

weight index information on the SbTMVP candidate may be derived as 0. That is, the weight

index information on the SbTMVP candidate may be derived as 0. Here, the weight index

direction and the Li prediction direction in bi-prediction) are the same.

[303] Alternatively, for example, the candidates may include the SbTMVP candidate, and

the weight index information may be derived based on weight index information on a center

be derived based on the weight index information on the center block in the col block. Here,

the collocated block may include a block at the same position as the current block in a reference picture different from the current picture in which the current block is positioned, and the center block may include a bottom-right subblock among four subblocks located in the center of the collocated block.

[304] Alternatively, for example, the candidates may include the SbTMVP candidate, and

the weight index information may be derived based on weight index information on each of

may be derived based on the weight index information on each of the subblocks of the col

block.

[305] Although not illustrated in FIG. 12, for example, the decoding apparatus may derive

residual samples based on residual-related information included in the image information.

Also, the decoding apparatus may generate reconstructed samples based on the prediction

samples and the residual samples. A reconstructed block and a reconstructed picture may be

derived based on the reconstructed samples.

[306] For example, the decoding apparatus may obtain image information including all or

parts of the above-described pieces of information (or syntax elements) by decoding the

bitstream or the encoded information. Further, the bitstream or the encoded information may

be stored in a computer readable storage medium, and may cause the above-described decoding

method to be performed.

[307] Although methods have been described on the basis of a flowchart in which steps or

blocks are listed in sequence in the above-described embodiments, the steps of the present

document are not limited to a certain order, and a certain step may be performed in a different

step or in a different order or concurrently with respect to that described above. Further, it will

be understood by those ordinary skilled in the art that the steps of the flowcharts are not

exclusive, and another step may be included therein or one or more steps in the flowchart may

be deleted without exerting an influence on the scope of the present disclosure.

[308] The aforementioned method according to the present disclosure may be in the form of

software, and the encoding apparatus and/or decoding apparatus according to the present

disclosure may be included in a device for performing image processing, for example, a TV, a

computer, a smart phone, a set-top box, a display device, or the like.

[309] When the embodiments of the present disclosure are implemented by software, the

aforementioned method may be implemented by a module (process or function) which

performs the aforementioned function. The module may be stored in a memory and executed

by a processor. The memory may be installed inside or outside the processor and may be

connected to the processor via various well-known means. The processor may include

Application-Specific Integrated Circuit (ASIC), other chipsets, a logical circuit, and/or a data

processing device. The memory may include a Read-Only Memory (ROM), a Random

Access Memory (RAM), a flash memory, a memory card, a storage medium, and/or other

storage device. In other words, the embodiments according to the present disclosure may be

implemented and executed on a processor, a micro-processor, a controller, or a chip. For

example, functional units illustrated in the respective figures may be implemented and executed

on a computer, a processor, a microprocessor, a controller, or a chip. In this case, information

on implementation (for example, information on instructions) or algorithms may be stored in a

digital storage medium.

[310] In addition, the decoding apparatus and the encoding apparatus to which the

embodiment(s) of the present document is applied may be included in a multimedia

broadcasting transceiver, a mobile communication terminal, a home cinema video device, a

digital cinema video device, a surveillance camera, a video chat device, and a real time

communication device such as video communication, a mobile streaming device, a storage

medium, a camcorder, a video on demand (VoD) service provider, an Over The Top (OTT)

video device, an internet streaming service provider, a 3D video device, a Virtual Reality (VR) device, an Augment Reality (AR) device, an image telephone video device, a vehicle terminal

(for example, a vehicle (including an autonomous vehicle) terminal, an airplane terminal, or a

ship terminal), and a medical video device; and may be used to process an image signal or data.

For example, the OTT video device may include a game console, a Bluray player, an Internet

connected TV, a home theater system, a smartphone, a tablet PC, and a Digital Video Recorder

(DVR).

[311] In addition, the processing method to which the embodiment(s) of the present

document is applied may be produced in the form of a program executed by a computer and

may be stored in a computer-readable recording medium. Multimedia data having a data

structure according to the embodiment(s) of the present document may also be stored in the

computer-readable recording medium. The computer readable recording medium includes all

kinds of storage devices and distributed storage devices in which computer readable data is

stored. The computer-readable recording medium may include, for example, a Bluray disc

(BD), a universal serial bus (USB), a ROM, a PROM, an EPROM, an EEPROM, a RAM, a

CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device. The computer

readable recording medium also includes media embodied in the form of a carrier wave (for

example, transmission over the Internet). In addition, a bitstream generated by the encoding

method may be stored in the computer-readable recording medium or transmitted through a

wired or wireless communication network.

[312] In addition, the embodiment(s) of the present document may be embodied as a

computer program product based on a program code, and the program code may be executed

on a computer according to the embodiment(s) of the present document. The program code

may be stored on a computer-readable carrier.

[313] FIG. 14 represents an example of a contents streaming system to which the

embodiment of the present document may be applied.

[314] Referring to FIG. 14, the content streaming system to which the embodiments of the

present document is applied may generally include an encoding server, a streaming server, a

web server, a media storage, a user device, and a multimedia input device.

[315] The encoding server functions to compress to digital data the contents input from the

multimedia input devices, such as the smart phone, the camera, the camcorder and the like, to

generate a bitstream, and to transmit it to the streaming server. As another example, in a case

where the multimedia input device, such as, the smart phone, the camera, the camcorder or the

like, directly generates a bitstream, the encoding server may be omitted.

[316] The bitstream may be generated by an encoding method or a bitstream generation

method to which the embodiments of the present document is applied. And the streaming server

may temporarily store the bitstream in a process of transmitting or receiving the bitstream.

[317] The streaming server transmits multimedia data to the user equipment on the basis of

a user's request through the web server, which functions as an instrument that informs a user

of what service there is. When the user requests a service which the user wants, the web server

transfers the request to the streaming server, and the streaming server transmits multimedia

data to the user. In this regard, the contents streaming system may include a separate control

server, and in this case, the control server functions to control commands/responses between

respective equipment in the content streaming system.

[318] The streaming server may receive contents from the media storage and/or the encoding

server. For example, in a case the contents are received from the encoding server, the contents

may be received in real time. In this case, the streaming server may store the bitstream for a

predetermined period of time to provide the streaming service smoothly.

[319] For example, the user equipment may include a mobile phone, a smart phone, a laptop

computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable

multimedia player (PMP), a navigation, a slate PC, a tablet PC, an ultrabook, a wearable device

(e.g., a watch-type terminal (smart watch), a glass-type terminal (smart glass), a head mounted

display (HMD)), a digital TV, a desktop computer, a digital signage or the like.

[320] Each of servers in the contents streaming system may be operated as a distributed

server, and in this case, data received by each server may be processed in distributed manner.

[321] Claims in the present description can be combined in a various way. For example,

technical features in method claims of the present description can be combined to be

implemented or performed in an apparatus, and technical features in apparatus claims can be

combined to be implemented or performed in a method. Further, technical features in method

claim(s) and apparatus claim(s) can be combined to be implemented or performed in an

apparatus. Further, technical features in method claim(s) and apparatus claim(s) can be

combined to be implemented or performed in a method.

Claims

What is claimed is:

1. An image decoding method performed by a decoding apparatus, comprising:

receiving image information including inter-prediction mode information and inter

prediction type information through a bitstream;

generating a merge candidate list of a current block based on the inter-prediction mode

information;

selecting one candidate from among the candidates included in the merge candidate list;

deriving an inter-prediction type of the current block as a bi-prediction based on the

inter-prediction type information;

deriving motion information on the current block based on the selected candidate;

generating LO prediction samples and Li prediction samples of the current block based

on the motion information; and

generating prediction samples of the current block based on the LO prediction samples,

the Li prediction samples, and weight information, wherein the weight information is derived

based on weight index information on the selected candidate,

wherein the candidates include an affine merge candidate, and the affine merge

candidate includes control point motion vectors (CPMV),

when the affine merge candidate includes a CPMV for control point 0 (CPO) positioned

at a top-left of the current block, the weight index information on the affine merge candidate is

the CPO, and

when the affine merge candidate does not include the CPMV for the CPO positioned at

the top-left of the current block, weight index information on the affine merge candidate is

derived based on weight index information on a specific block among neighboring blocks of control point 1 (CP1) positioned at a top-right of the current block.

2. The image decoding method of claim 1, wherein the specific block among the

neighboring blocks of the CPO corresponds to a block used for deriving the CPMV for the CPO,

and

the neighboring blocks of CPO include a top-left corner neighboring block of the current

block, a left neighboring block adjacent to a bottom of the top-left corner neighboring block,

and a top neighboring block adjacent to a right of the top-left corner neighboring block.

3. The image decoding method of claim 1, wherein the specific block among the

neighboring blocks of the CP1 corresponds to a block used for deriving the CPMV for the CP1,

and

the neighboring blocks of the CP Iinclude a top-right corner neighboring block of the

current block and a top neighboring block adjacent to a left of the top-right corner neighboring

block.

4. The image decoding method of claim 1, wherein the candidates include a pair-wise

candidate, and the pair-wise candidate is derived based on the other two candidates among the

candidates, and

weight index information on the pair-wise candidate is derived based on weight index

information on one of the two candidates.

5. The image decoding method of claim 1, wherein the candidates include a pair-wise

candidate, and the pair-wise candidate is derived based on other two candidates among the

candidates, when the weight index information on each of the other two candidates is the same as the first weight index information, the weight index information on the pair-wise candidate is derived based on the first weight index information, when the weight index information on each of the other two candidates is not the same, the weight index information on the pair-wise candidate is derived based on default weight index information, and the default weight index information corresponds to weight index information assigning the same weight to each of the LO prediction samples and the L prediction samples.

6. The image decoding method of claim 1, wherein the candidates include a pair-wise

candidates,

when the weight index information on each of the other two candidates is the same as

the first weight index information, the weight index information on the pair-wise candidate is

derived based on the first weight index information,

when the weight index information on each of the other two candidates is not the same,

the weight index information is derived based on weight index information rather than the

default weight index information among the weight index information on each of the other two

candidates, and

the default weight index information corresponds to weight index information assigning

the same weight to each of the LO prediction samples and the L prediction samples.

7. The image decoding method of claim 1, wherein the candidates include a subblock

based temporal motion vector prediction (SbTMVP) candidate, and

the weight index information on the SbTMVP candidate is derived based on the weight index information on the left neighboring block of the current block.

8. The image decoding method of claim 1, wherein the candidates include a subblock

based temporal motion vector prediction (SbTMVP) candidate, and

the weight index information on the SbTMVP candidate is derived as 0.

9. The image decoding method of claim 1, wherein the candidates include a subblock

based temporal motion vector prediction (SbTMVP) candidate,

the weight index information on the SbTMVP candidate is derived based on weight

index information on a center block in a col block,

the col block includes a block in the same position as the current block in a reference

picture different from a current picture in which the current block is positioned, and

the center block includes a bottom-right subblock among four subblocks positioned at

a center of the col block.

10. The image decoding method of claim 1, wherein the candidates include a subblock

based temporal motion vector prediction (SbTMVP) candidate,

the weight index information on the SbTMVP candidate is derived based on weight

index information on each of the subblocks in a col block, and

picture different from a current picture in which the current block is positioned.

11. The image decoding method of claim 1, wherein the candidates include a temporal

merge candidate, and

weight index information on the temporal merge candidate is derived as 0.

12. The image decoding method of claim 1, wherein the candidates include a temporal

merge candidate,

the weight index information on the temporal merge candidate is derived based on

weight index information on a col block, and

13. An image encoding method performed by an encoding apparatus, comprising:

determining an inter-prediction mode of the current block and generating inter

prediction mode information indicating the inter-prediction mode;

generating a merge candidate list of the current block based on the inter-prediction

mode information;

generating selection information indicating one of candidates included in the merge

candidate list;

generating inter-prediction type information indicating an inter-prediction type of the

current block as bi-prediction; and

encoding image information including the inter-prediction mode information, the

selection information, and the inter-prediction type information,

wherein the candidates include an affine merge candidate, and the affine merge

candidate includes control point motion vectors (CPMV),

indicated based on weight index information on a specific block among neighboring blocks of

the CPO, and when the affine merge candidate does not include the CPMV for the CPO positioned at the top-left of the current block, weight index information on the affine merge candidate is indicated based on weight index information on a specific block among neighboring blocks of control point 1 (CP1) positioned at a top-right of the current block.

14. A computer-readable storage medium storing encoded information causing an

image decoding apparatus to perform an image decoding method, the image decoding method

comprising:

obtaining image information including inter-prediction mode information and inter

prediction type information through a bitstream;

information;

inter-prediction type information;

on the motion information; and

based on weight index information on the selected candidate,

wherein the candidates include an affine merge candidate, and the affine merge

candidate includes control point motion vectors (CPMV),

at a top-left of the current block, the weight index information on the affine merge candidate is derived based on weight index information on a specific block among neighboring blocks of the CPO, and when the affine merge candidate does not include the CPMV for the CPO positioned at the top-left of the current block, weight index information on the affine merge candidate is derived based on weight index information on a specific block among neighboring blocks of control point 1 (CP1) positioned at a top-right of the current block.